記述言語：英語   出版者・発行元：AMER INST PHYSICS  

Fluorescence excitation spectra of the S-1-S-0 origin band of 9-cyanoanthracene have been observed under a uniform electric field up to 200 kV/cm to explore pendular-state spectrum of an asymmetric-top molecule close to the strong field limit. The observed spectra exhibit distinct evolution of the band contour as a function of the applied electric field, which are much different from each other for different excitation configurations. An approximate method suitable for spectrum simulations of large asymmetric-top molecules in a pendular condition is developed for the analysis of the experimental results. The comparison of the observed and simulated spectra shows that the spectra are well ascribed in terms of the pendular-state selection rules, which have recently been derived from theoretical consideration of the pendular-limit representation of energy levels and spectra [R. Kanya and Y. Ohshima, Phys. Rev. A 70, 013403 (2004)]. (C) 2004 American Institute of Physics.

DOI： 10.1063/1.1806420

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記述言語：英語   出版者・発行元：AMERICAN PHYSICAL SOC  

We report theoretical investigations pertaining to spectroscopy of pendular-state molecules, which are subjected to the large electrostatic interaction between the molecular dipole and a strong external field. After an appropriate coordinate transformation and a power-series expansion with an order parameter lambda that represents the degree of pendular condition, the zeroth-order Hamiltonian for the pendular limit has been derived. Motions of asymmetric tops in a high field are well described as two-dimensional anisotropic harmonic oscillations, and pendular-state quantum numbers have been introduced to label the energy levels. By using perturbative treatments, energies up to the lambda(0) order are represented analytically with the pendular-state quantum numbers. Symmetry considerations are also accomplished by using the group theory appropriate to dipolar rigid bodies of symmetric and asymmetric tops in a uniform electric field. Energy levels and wave functions are classified into irreducible representations of the groups and selection rules for optical transitions are described. Energy-level correlations between the field-free and pendular conditions are also discussed on the basis of the group theoretical considerations. For symmetric and asymmetric tops, pendular-limit selection rules on the quantum numbers are derived by expanding the transition-dipole operators on lambda, and transition strengths are analytically evaluated for all the excitation configurations with each of the transition types. Utilities of the present formulation have been verified by the comparison with exact model calculations based on the matrix diagonalization with a free-rotation basis set.

DOI： 10.1103/PhysRevA.70.013403

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記述言語：英語   出版者・発行元：ROYAL SOC CHEMISTRY  

Fluorescence excitation and ultra violet-ultraviolet hole burning spectra of jet-cooled anthracene-ammonia clusters were observed. The SI-So origin of the 1 : 1 complex shows doublet bands, which were assigned to those in the ground and the first excited states of the internal rotation associated with the ortho and para hydrogen nuclear spin states of NH3, respectively. The ammonia molecule is located above the centre of the aromatic plane with a centre-of-mass distance of 3.6 Angstrom, which is typical of a pi hydrogen bonded aromatic complex. The rotational contour of the internal rotation excited state was analyzed with an effective Hamiltonian including the coupling between the internal and end-over-end rotations, to show that the internal rotation angular momentum is partially quenched because of the potential anisotropy for rotation around the axis that connects the centres of mass of ammonia and anthracene.

DOI： 10.1039/b305673b

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

The change (Deltamu) in the permanent dipole moment on the S,, So electronic excitation is determined for Coumarin 153 (C 153) in a molecular beam from the spectral change induced by applying a strong dc electric field up to 200 Mcm. The comparison of the observed fluorescence excitation spectra under various external fields with the corresponding simulations for a pendular-state molecule yields Deltamu = 7.1+/-0.4 D for both the syn and anti conformers of C153. Previous experimental results on Deltamu in the condensed phase, as well as the theoretical predictions reported in the literature, are discussed on the basis of the present value under an isolated condition. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(03)00075-7

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記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

DOI： 10.1021/ja028522x

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記述言語：英語  

The S1-S0bands that were assigned to neutral benzene trimer were reported. It was found that there were five isotopomers which indicated that the four benzene sites were equivalent in the cluster. The fragmentation of tetramer following resonantly enhanced two-photon ionization (R2PI) by loss of a benzene molecule was found to be efficient even in two-color (R2PI) condition.

DOI： 10.1063/1.1494976

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

We report the reinvestigation of the S-1-S-0 electronic transitions of (benzene)(n) clusters by two-color mass-selective resonantly enhanced two-photon ionization (R2PI) and UV-UV (ultraviolet) hole burning spectroscopies. The present paper describes the band system that has been assigned to the trimer for two decades. Hole burning measurements by monitoring the trimer ion isotopomer channels in the expansion of a mixture of C6H6 and C6D6 have shown the contribution of six spectral carriers in the R2PI spectra, two of which are isotopically pure clusters. The other hetero isotopic species containing at least one C6H6 moiety appear in two adjacent isotopomer channels. It is argued that the band system should be reassigned to the neutral tetramer having four equivalent sites, which are detected in daughter ion mass channels due to efficient fragmentation after ionization even with two-color excitation. The experimental results are consistent with a distorted tetrahedral structure with S-4 symmetry predicted as the global minimum by several model calculations. This conclusion is further supported by an analysis of exciton splittings in the C6H6-localized origin band, and this analysis provides coupling constants for the excitation exchange in the S-1 state. Other experimental results reported so far pertaining to this species are reconsidered on the basis of the new assignment. (C) 2002 American Institute of Physics.

DOI： 10.1063/1.1494976

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

We present a reexamination of the S-1-S-0 transition of the (benzene)(n) cluster that appears only in the dimer ion channel and thus has been assigned to an isomer of the neutral dimer other than the extensively studied T-shaped form. Mass-selective resonantly enhanced two-photon ionization (R2PI) excitation and UV-UV (ultraviolet) hole burning spectra are measured in the 0(0)(0) and 6(0)(1) vibronic regions. It is established from the observed spectra monitoring three isotopomer channels, (C6H6)(2)(+), [(C6H6)(C6D6)](+), and (C6D6)(2)(+), that efficient fragmentation following ionization prohibits one to observe the two-color R2PI spectra in the parent ion channels, similar to the case for the benzene tetramer as presented in Paper I [J. Chem. Phys. 117, 3656 (2002)]. Three neutral isotopomers containing at least one C6H6 moiety are identified, and this result argues the reassignment of the band system to the neutral benzene trimer with a cyclic form, where the three benzene sites are equivalent. The spectra of the homo isotopomers [(C6H6)(3) and (C6D6)(3)] in the two vibronic regions exhibit small splittings due to the excitation exchange interactions, and this observation is discussed on the symmetry of the cluster geometry. Energetics pertaining to neutral and ionic benzene clusters are also discussed with previous experimental studies to assess a reason of the efficient fragmentation in the ionic states after R2PI for the trimer and larger clusters but not for the dimer. (C) 2002 American Institute of Physics.

DOI： 10.1063/1.1494977

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記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Structures of 9-cyanoanthracene (CNA) clusters microsolvated with a single molecule of aprotic solvents (carbon dioxide, two isotopomers of acetonitrile, and fluoroform) have been studied by rotational coherence spectroscopy (RCS) implemented with the time-resolved fluorescence depletion method. All of the observed RCS traces exhibit pronounced C-type transients, and this fact suggests that these species are quite close to planar asymmetric tops with their electronic transition moments pointing to in-plane directions. Weak J-type transients have been also identified for CNA-CO2 and -CF3H, the latter of which shows A-type transients as well. By comparing the experimental observations with density functional theory calculations at the B3LYP/6-31G(d,p) level, it is concluded that the solvent molecule is located by the side of the CN group of CNA with its molecular axis lying in the CNA molecular plane. All of the cluster geometries are of C, symmetry, in which a positively charged atom of the solvents (C, H, or H for CO2, CH3CN, and CF3H, respectively) is close to the cyano nitrogen of CNA, while an electonegative part (O, N, or F) contacts with the 1-position hydrogen of CNA. Some geometrical parameters including the centers of mass separation are obtained from the RCS-derived rotational constants.

DOI： 10.1021/jp0102771

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

The (A) over tilde (3)Pi (i)<--(X) over tilde (3)Sigma (-) electronic transition of a carbon-chain molecule CCS has been observed for the first time by laser induced fluorescence spectroscopy. The species was generated with a pulsed discharge of 0.5% C2H2 and 0.5% CS2 diluted in Ar via a pulsed supersonic jet. A number of bands in the 690-675 nm and 600-615 nm regions (14 500-14 800, 16 200-16 600 cm(-1)) were observed and assigned to those of CCS using ground state combination differences. Three of the bands in each region were found to belong to the three (A) over tilde (3)Pi (i) spin-orbit components of the (A) over tilde (3)Pi (i)<--X (3)Sigma (-) transition (T-v=14 662.777(4) and 16 423 cm(-) (1)), and an effective set of rotational constants for the upper states were obtained. The higher energy band was heavily perturbed, preventing the determination of effective constants for this band. These bands have been tentatively assigned as two successive bands in the (A) over tilde (3)Pi (i)(n,0,0) progression with a resultant effective value of 1760 cm(-1) for the (A) over tilde (3)Pi (i) nu (1) vibrational fundamental. Dispersed fluorescence spectra from the (A) over tilde (3)Pi (i)<--X (3)Sigma (-) band of CCS have also been observed, yielding definitive experimental information on the vibrational structure of the X (3)Sigma (-) ground state for the first time. The three harmonic frequencies were determined to be 1708.2(40) cm(-1), 862.5(19) cm(-1), and 269.3(13) cm(-1) for omega (1) (CC stretch), omega (2) (CS stretch), and omega (3) (CCS bend), respectively. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1356006

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記述言語：英語  

DOI： 10.1063/1.1356006

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

The vibronic band systems of (benzene)(n) clusters in the S-1-S-0 region are revisited by mass-selective resonant two-photon ionization and ultraviolet-ultraviolet hole burning spectroscopies. A detailed examination of the spectra of isotopomers composed of C6H6 and C6D6 reveals that there is substantial fragmentation following photoionization for the trimer and the tetramer. Transitions which have been assigned to the trimer are most probably due to the tetramer. Instead, reassigned to the trimer is the band system which has been believed to be of an isomeric form of the dimer. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1349081

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

Rotational coherence spectroscopy (RCS) has been applied to determine the rotational constants of the two isotopic species of the 9-cyanoanthracene (CNA)-water complex, CNA-H2O, and CNA-D2O. To support the experimental observation, DFT calculations at the B3LYP/6-31G(d,p) level have been also performed to identify several stable conformations. The structure of the complex is found to be such that water is hydrogen-bonded to the pi -electrons of the cyano group of CNA. Geometrical parameters consistent with the experimental results are evaluated. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(00)01446-9

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記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Rotational coherence spectroscopy implemented with time-resolved fluorescence depletion has been applied in a structural study of 9-cyanoanthracene (CNA) and its clusters with Ar up to three atoms. For bare CNA, C-type transients for the S-1 and S-0 states have been observed separately, yielding independent sets of rotational constants for the two states. For the Ar clusters, rotational constants as averages for S-1 and S-0 have been derived to fix the cluster geometry. The Ar atom in CNA-Ar is located 3.46 +/- 0.03 Angstrom above the central aromatic ring of CNA and displaced slightly from the ring center toward the cyano group. The plane-Ar distance is quite close to those in clusters with other polycyclic aromatic molecules. Two values (similar to0.2 or 0.6 Angstrom) for the displacement to the cyano group are consistent with the experimental data, and results on related aromatics-Ar show that the former is preferable. The dominant conformer of CNA-(Ar)(2) has been determined as a two-sided (1 + 1)-type: structures for each sides of the CNA plane are the same as that of CNA-Ar within the experimental uncertainties. CNA-(Ar)(3) has a (2 + 1)-type structure: one side of the substrate is the same as CNA-Ar, and an Ar dimer lies 3.48 +/- 0.04 ii above the other side. The determined conformations of CNA-(Ar)(1,3) are the same as those of the corresponding anthracene clusters, but that of CNA-(Ar)(2) is in contrast to that of anthracene-(Ar)(2), which has been identified as a (2 + 0)-type. Model potential calculations have been employed to explain the difference in structural motifs of the two closely related clusters.

DOI： 10.1021/jp0035378

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DOI： 10.1063/1.1349081

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DOI： 10.1021/jp0035378

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DOI： 10.1016/S0009-2614(00)01446-9

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記述言語：英語  

DOI： 10.1063/1.1322364

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

Rotational spectra of the Ar-SH((2)Pi (i)) radical complex and its deuterated species have been studied using a Fourier-transform microwave spectrometer. The complexes are produced in a supersonic free jet using a pulsed discharge of H2S or D2S diluted in Ar. R-branch transitions in the lower spin component (Omega =3/2) for the linear (2)Pi (i) radical were observed for J"=1.5-7.5 in the 8-26 GHz region, in which the parity doublings and hyperfine splittings associated with the H/D nuclei have been observed. Effective rotational constants for Ar-SH and Ar-SD are determined to be 1569.660(3) and 1567.723(4) MHz, respectively, using an effective (2)Pi Hamiltonian including hyperfine terms. An effective centrifugal distortion constant, D, has been determined to be negative. A two-dimensional intermolecular potential energy surface for the Ar-SH((2)Pi (i)) complex has been derived from a least-squares fitting of the observed rotational transitions, where several parameters are constrained to the values from an ab initio calculation at the RCCSD(T)/aug-cc-pVQZ level. The average potential turned out to be fairly isotropic with two shallow minima corresponding to the linear Ar . . . SH and Ar . . . HS configurations, among which the former is 7.2 cm(-1) more stable than the latter. The determined equilibrium distance between Ar and the SH center-of-mass is 3.791 Angstrom at the Ar . . . SH global minimum configuration. The vibrational ground state is located above the barrier of only about 20 cm(-1) between the two minima, and its wave function is widely spread along the bending coordinate. The negative sign of the effective D constant is well explained by the enhancement of the probability at the linear Ar . . . SH configuration by the centrifugal force, which results in a decrease of the vibrationally averaged Ar-SH intermolecular distance. (C) 2000 American Institute of Physics. [S0021- 9606(00)00946-6].

DOI： 10.1063/1.1322364

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記述言語：英語   出版者・発行元：American Chemical Society  

A series of papers (I-III) reports spectroscopic investigation on structure and dynamics of 9(10H)-acridone (AD) and its hydrated clusters. As the first part of the series, the present paper describes their lowest 1(π,π*) electronic transition in the 370-400 nm region studied by fluorescence-based laser spectroscopy and massselective two-color resonance-enhanced two-photon ionization (2C-R2PI). Thirteen fluorescent hydrates as well as the monomer have been identified in fluorescence-excitation and UV-UV hole-burning measurements, and size assignments for relatively smaller clusters, AD-(H2O)n (n = 1-6), have been conducted by 2C-R2PI. The origin bands for larger-size clusters show larger red shifts converging at ca. 2200 cm-1 but the changes are nonmonotonic, with a substantial increase from n = 2 to 3. Density-functional-theory (DFT) calculations at the B3LYP/6-31G(d,p) level have predicted that the energy difference between the C=O and N-H bonded isomers is quite small (only ≈ 1 kcal/mol) for n = 1 and 2. The observed spectral shifts of fluorescent hydrates with n = 1 and 2 are well reproduced by the HOMO-LUMO gap in the DFT orbital energies of either of the N-H or C=O bonded isomers, leaving the definitive structural assignments to fluorescence-detected infrared spectroscopy which will be described in paper II. For the larger clusters (n = 3-5), several minimum-energy structures have been identified within 2 kcal/mol in binding energy, among which the conformers with water molecules bridging between the C=O and N-H sites over the AD's aromatic rings are identified as the observed species, based on good agreement between the calculated and observed spectral shifts. © 2000 American Chemical Society.

DOI： 10.1021/jp001047+

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記述言語：英語   出版者・発行元：American Chemical Society  

As the final part of the series, nonradiative dynamics and energy-level structure of relevant electronic excited states in 9(10H)-acridone (AD) and its hydrated clusters have been studied by various spectroscopic methods. Time-resolved fluorescence measurements on their 1(π,π*) origin excitation have revealed that the fluorescence decay is very fast (≈10 ps) for bare AD but drastically lengthened (ns) in AD-(H2O)n (n = 1-6 and higher). Bare AD has been observed clearly by mass-selective delayed ionization and sensitizedphosphorescence detection, which indicates the efficient formation of molecules in triplet manifold after the 1(π,π*) excitation. Several weak peaks have been identified around each 1(π,π*) vibronic band of bare AD, and they are attributed to 3(π,π*) transitions which borrow intensity from the nearby 1(π,π*) bands through the direct spin-orbit coupling. Such satellite bands completely disappear in the fluorescent cluster spectra with n ≥ 1. All of the experimental observations indicate that the dominant nonradiative pathway in bare AD is the Si(π,π*) → T2(n,π*) intersystem crossing (ISC) followed by the T2(n,π*) -T1(π,π*) internal conversion. This direct ISC process becomes prohibited by the energy-level inversion between the S1 and T2 states induced by the H bonding to the C=O site. Thus the relaxation pathway is "switched" to the second-order ISC [Si(π,π*) → T1(π,π*)] in the fluorescent hydrated clusters, where the carbonyl site is involved in H-bonding networks. Owing to the increasing S1-T2 separation, the fluorescence quantum yield becomes larger for the higher clusters, which is approaching to the bulk solution value, i.e., Φf ≈ 1. The (π,π*) and (n,π*) shifts at each cluster geometry have been calculated as (N)HOMO-LUMO gaps in DFT orbital energies to support the picture on the energy-level structure. Most importantly, a small falloff in the fluorescence decay constants from H = 2 to 3 has been definitely correlated to the crossover in H-bonding topologies (the C=O bonded - the bridged form), which has already been established in papers I and II. The delayed ionization has identified new spectral features that are completely absent in the fluorescence excitation spectrum. They are assigned to the N-H bonded isomer(s) with n ≤ 3, which is at least as stable as the C=O bonded conformer(s) with the same size. The ISC in the hydrate(s) should be as fast as in bare AD, because of the lack of the S1-T2 level inversion. These experimental findings demonstrate the site-specific solvation effects on the electronic energy-level structure and the resultant nonradiative dynamics in the hydrated clusters of a bifunctional molecule. © 2000 American Chemical Society.

DOI： 10.1021/jp001049u

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記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

The present paper represents fluorescence-detected infrared measurements of 9(10H)-acridone (AD) and 10 of its fluorescent hydrated clusters, AD-(H2O), (n = 1-5 and more), which have been performed by monitoring the fluorescence from their (1)(pi,pi*) electronic origin transitions reported in paper I. In the n = 1 and 2 clusters, free N-H stretching band has been identified in addition to O-H stretching bands characteristic to water molecules acting as single proton donors. As the next solvation step, the II-bonded O-H stretches are further developed in the red-shifted region and the N-H stretch becomes involved in the hydrogen-bonds for the n = 3-5 clusters. For n greater than or equal to 6, more than one pair of double-donor O-H stretches appear. These spectral features are well correlated to the stepwise evolution in the hydrogen-bonding networks in AD-(H2O)(n), which have been predicted by the (pi,pi*) spectral-shift analysis and DFT calculations presented in paper I: water units are bound to the C=O site for n = I and 2, a single water chain bridges between the C=O and N-H sites above the AD aromatic rings for n = 3-5, and water bridges become branched for n greater than or equal to 6 and probably form three-dimensional cages at higher aggregation levels. Differences in hydrogen-bonding topologies, stabilities, and dynamical behaviors among the conformers are discussed on the basis of the experimental observations, the DFT calculations, and comparison with other hydrated aromatic clusters.

DOI： 10.1021/jp0010482

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

The vibrational spectra of supersonically cooled acridine-(H2O)(n) (n = 1-3) clusters in the electronic ground state have been measured by fluorescence-detected infrared spectroscopy. The observed O-H stretching fundamentals of the solvent have been analyzed with the aid of density functional theory calculations, to assign the structures of the clusters. In the It = I cluster, the water molecule acts as a proton donor which is hydrogen-bonded to the N atom of acridine. The second (third) water in the higher clusters is further hydrogen-bonded to the first (second) one to form a linear 'water chain', which surrounds an of the acridine molecule approximately in the plane of the aromatic ring. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(99)01386-X

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DOI： 10.1039/a910327i

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DOI： 10.1039/a910327i

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

Pure rotational spectra of N-14(2) .. CO, (NN)-N-15-N-14 .. CO, and N-15(2) .. CO have been observed using a Fourier transform microwave spectrometer. Two sets of transitions with J = 2 <-- 1, 3 <-- 2, and 4 <-- 3 were observed for N-14(2) .. CO and N-15(2) .. CO; transitions with smaller effective rotational constants B were stronger than those with larger B for the N-14(2) .. CO complex, while the opposite was observed for N-15(2) .. CO. It was concluded that for N-14(2) .. CO the first set corresponds to the K = 0 stack of ortho-N-2 and the second to K = 1 of para-N-2 based on a previous infrared analysis, hyperfine splittings, and the spin statistical weights. In the case of (NN)-N-15-N-14 .. CO, only one set was observed because of the lack of symmetry. The electric quadrupole coupling constant of N-14 is much smaller, while the centrifugal distortion constant is much larger, than those of related complexes. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(99)01225-7

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記述言語：英語  

DOI： 10.1016/S0009-2614(99)01225-7

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

Rotational spectra of tropolone in the ground vibronic state were measured by microwave spectroscopy. Due to the proton tunneling motion, the ground state is split into a doublet, of which the lower and upper components are denoted by 0(+) and 0(-), respectively. In the frequency region 28-84 GHz, more than 150 pure rotational transitions obeying a-type selection rules were observed for each of the 0(+) and 0(-) states. Additionally, tunneling-rotation transitions connecting the lower (0(+)) and upper (0(-)) components of the tunneling doublet were observed by pulsed Fourier transform microwave spectroscopy. Twenty-three P- and Q-branch lines were observed in the frequency region of 10-18 GHz, and analyzed combined with the pure rotational transitions for each of the 0(+) and 0(-) states. The proton tunneling splitting in the ground state, Delta(0) = 29 193.788 +/- 0.026 MHz, and the tunneling- rotation interaction constant F = 16.456 +/- 0.015 MHz, were determined, as well as the rotational and centrifugal distortion constants. The dipole moment along the a axis, responsible for the rotational transitions, was determined to be 3.428 +/- 0.050 and 3.438 +/- 0.050 D for the 0(+) and 0(-) states, respectively. (C) 1999 American Institute of Physics. [S0021-9606(99)01104-6].

DOI： 10.1063/1.477863

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

The first spectroscopic identification of a van der Waals complex containing salt, Ar-NaCl, has been reported. A cm-region rotational spectrum of the complex has been observed for the Cl-35 and Cl-37 isotopomers by using a Fourier-transform microwave spectrometer combined with a laser ablation nozzle source. The vibrationally averaged geometry of the complex is of the linear Ar Na-CI configuration, with the internuclear distance of R(Ar ... Na) = 2.887 Angstrom. An almost fully resolved hyperfine structure in low-J transitions has yielded precise nuclear quadrupole coupling constants associated with both Na and Cl nuclei, which indicate a substantial charge rearrangement in the NaCl molecule by complexation with Ar. (C) 1998 American Institute of Physics. [S0021-9606(98)03248-6].

DOI： 10.1063/1.477754

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

Laser-induced fluorescence (LIF) spectra of the C4H radical and its isotopomer C4D have been observed in a supersonic free jet expansion for the first time. The jet cooled free radicals have been generated in an electric discharge of 0.5% C2H2 or C2D2 in Ar using a pulsed discharge nozzle (PDN). Twenty and eighteen vibronic bands of C4H and C4D, respectively, have been observed in the 24 000-25 000 cm(-1) region. Most of the observed bands have been assigned as either (2) Pi-(2) Sigma or two types of (2) Sigma-(2) Sigma. Effective spin-orbit interaction constants were determined by analyses of the (2) Pi-(2) Sigma bands to be -14.7644(80) and -10.9926(35) cm(-1) for C4H and C4D, respectively, leading to conclusion that the upper electronic state of the observed band system is (B) over tilde (2) Pi(i), in agreement with a recent ab initio calculation by Sobolewski and Adamowicz [J. Chem. Phys. 102, 394 (1995)]. Observation of two types of (2) Sigma-(2) Sigma bands, (2) Sigma(+)-(2) Sigma(+) and (2) Sigma((+/-))-(2) Sigma(+), is explained by the difference of the magnitudes of Renner-Teller interactions for the bending vibrational modes involved. We were able to assign the nu(5) (CCH bending) and nu(6) (CCC bending) progressions of the (B) over tilde (2) Pi(i) state, where the Renner-Teller interaction is large for nu(5), and small for nu(6). The vibrational frequencies and the Renner parameters were determined to be omega(5)=344 cm(-1), epsilon(5) = -0.657, omega(6) = 189.3 cm(-1), and epsilon(6) = -0.0158 for C4H, and omega(5) = 295 cm(-1), epsilon(5) = -0.692, omega(6) = 183.4 cm(-1), and epsilon(6) = -0.0188 for C4D, respectively. Intensities of the symmetry forbidden (2) Sigma-(2) Sigma bands were larger than those of the symmetry allowed (2) Pi-(2) Sigma bands, suggesting a very small energy gap and strong vibronic mixing between the (A) over tilde (2) Pi-(2) Sigma and (X) over tilde (2) Sigma(+) states. Fluorescence lifetime profiles exhibited fast decay (10-20 ns) followed by a very weak and slow decay (3-4 mu s) component with complicated beat structures. The implication is that C4H in the (B) over tilde (2) Pi(i) state has a fast relaxation path to nonradiative states through internal conversion, and therefore does not dissociate under near uv radiation at 400-417 nm. (C) 1998 American Institute of Physics. [S0021-9606(98)02209-0].

DOI： 10.1063/1.475746

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記述言語：英語   出版者・発行元：ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS  

The rotational spectrum of the argon-diacetylene van der Waals complex, produced in a supersonic molecular beam at 1 K, has been observed with a Fourier-transform microwave spectrometer. We observed 22 a-type rotational transitions with K-a up to 3. Three rotational constants, five centrifugal distortion constants, and one higher-order centrifugal distortion constant were determined precisely by least-squares analysis. The complex is shown to have a planer T-shaped structure with C-2 nu symmetry. The structural analysis provides chat the Ar atom is located 3.68 A from the center of mass of diacetylene. Force constants for the van der Waals vibrations were determined from the centrifugal distortion constants. It has been found that this complex has a much steeper and more harmonic intermolecular potential than the argon-acetylene complex. (C) 1997 Academic Press.

DOI： 10.1006/jmsp.1997.7359

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

The rotational spectrum of the propargyl radical (H2CCCH) was recorded with Fourier-transform microwave (FTMW) spectrometer coupled with a pulsed discharge nozzle (PDN), Fine and hyperfine components belonging to the 1(01)-0(00), 2(02)-1(01), 2(12)-1(11), and 2(11)-1(01) rotational transitions in the B-2(1) ground vibronic state were observed. The analysis of the FTMW spectra resulted in the following ground-state molecular constants, with 3 sigma uncertainties given in parentheses. The rotational and centrifugal distortion constants are B-0=9523.6775(60) MHz, C-0=9206.8805(60) MHz, Delta(N)=3.44(63) kHz, and Delta(NK)=0.3753(28) MHz. The spin-rotation coupling constants are epsilon(aa)=-529.386(60), epsilon(bb)=-11.524(30), and epsilon(cc)=-0.520(32) MHz. The hyperfine coupling constants are a(F)=-36.323(24), T-aa=17.400(24), and T-bb=-17.220(37) MHz for the acetylenic (CH) proton, and a(F)=-54.21(11) and T-aa=-14.121(19) MHz for the methylenic (CH2) proton. The derived hyperfine coupling constants indicate comparable contributions of the allenyl (H2C=C=CH) and propargyl (H2C-C=CH) forms to the resonance structure [H-2(C) over dot-C=CH <----> H2C=C=(C) over dotH], (C) 1997 American Institute of Physics.

DOI： 10.1063/1.474631

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

Rotational spectra of four isotopomers of Ar-HCO+ have been studied in a jet-cooled condition by using a Fabry-Perot-type Fourier-transform microwave spectrometer. The ionic complex has a linear proton-bound form, with approximate intermolecular stretching and bending frequencies of 130 cm(-1) and 110 cm(-1), respectively. (C) 1997 American Institute of Physics.

DOI： 10.1063/1.473416

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DOI： 10.1063/1.473568

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DOI： 10.1063/1.473568

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

Rotation-vibration levels in the energy region near the HCP<->HPC (X) over tilde(1) Sigma(+) isomerization barrier (i.e., the HPC geometry) were observed by HCP (A) over tilde-(X) over tilde and (C) over tilde-(X) over tilde stimulated emission pumping (SEP) spectroscopy. Unlike HCN<->HNC, where the unstable isomer corresponds to a local minimum on the potential energy surface, the HPC isomer corresponds to a saddle point. In the (A) over tilde-(X) over tilde SEP spectra, the l=0 and 2 components of purl bend overtone levels (0,26 less than or equal to upsilon(2) less than or equal to 42,0) and the bend-CP stretch combination levels, (0,24,1) and (0,26,1), were sampled. On the other hand, in the (C) over tilde-(X) over tilde SEP spectra, which sample l=0 components exclusively, 2 omega(2):1 omega(3) polyads were identified. These polyads appeared in the SEP spectra as a regular, easily recognizable pattern. Since the (C) over tilde-(X) over tilde SEP spectra appeared to be almost totally Franck-Condon nonselective (a large fraction of the predicted total density of l=0 levels was observed), the polyad pattern was the key to vibrational assignments of highly excited vibrational levels. It was found that the bending vibration exhibits very regular (Morse-type) behavior up to at least upsilon(2)=42. However, an abrupt change was found in the upsilon(2)-dependence of all of the vibrational fine structure constants above upsilon(2) = 36, E((0,36,0)) = 22 048 cm(-1). In addition, a sudden turning on of perturbations in the pure bend overtone levels was also observed to occur at upsilon(2)=32. These abrupt changes in the level structure could be related to an abrupt change in curvature of the potential energy surface along directions perpendicular to the bending coordinate when the bending coordinate is far from equilibrium. (C) 1996 American Institute of Physics.

DOI： 10.1063/1.472601

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

Rotational spectra of the molecular ions HOCO+ and HOCS+, and the ion complexs, D-3(+)-Ar and sym-D2H+-Ar were observed in a supersonic-jet expansion by using a Fabry-Perot type Fourier-transform microwave spectrometer cooperated with a pulsed discharge nozzle. Ion-formation efficiency for HOCS+ relative to the parent molecule under applied conditions was estimated to be approximate to 10(-4). Tunneling splitting in the lowest rotational transition of D-3(+)-Ar was not resolved within the experimental linewidth of approximate to 100 kHz.

DOI： 10.1016/0009-2614(96)00500-3

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記述言語：英語   出版者・発行元：Elsevier  

LIF spectra of the à 2Πi-X̃ 2Πi transition of the HCCS radical were observed in a supersonic jet generated by using a pulsed-discharge nozzle. Adiabatic cooling yielded definitive rotational assignments for ≈ 40 vibronic bands. The fluorescence from single rovibronic levels exhibited a quantum beat in most of the observed bands. The number of beat components increased gradually with internal energy, approaching the limiting case for a 'large molecule'. The observed quantum interference is ascribed, based on the estimated densities of background states, to the internal conversion coupling with highly excited vibrational levels in the X̃ 2Πi state.

DOI： 10.1016/0009-2614(96)00272-2

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記述言語：英語  

DOI： 10.1016/0009-2614(96)00272-2

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記述言語：英語   出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE  

The lowest rotational transitions J = 1 <-- 0 of NaBH4 and KBH4 were observed, using a Fourier transform microwave spectrometer combined with a laser ablation apparatus. Hyperfine structure has been observed at good resolution yielding precise values of the nuclear quadrupole coupling constants eQq for both the alkali metal and boron atoms. The eQq values of the alkali metals, -3.385(31) and -4.256(29) MHz for M = Na-23 and K-39 in M(11)BH(4) respectively, are close to those in (NaCl)-Cl-35 (-5.6698 MHz) and (KCl)-Cl-35 (-5.656 MHZ), indicating that NaBH4 and KBH4 are also ionic molecules. The boron eQq's are small, -0.670(53) and -0.722(59) MHz for (NaBH4)-B-11 and (KBH4)-B-11 respectively, much smaller in magnitude than those reported for known boron-containing compounds, indicating that the BH4 group retains a structure of approximate T-d symmetry. (C) 1995 Academic Press, Inc.

DOI： 10.1006/jmsp.1995.0002

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

DOI： 10.1063/1.469626

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記述言語：英語  

DOI： 10.1006/jmsp.1995.1170

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

DOI： 10.1063/1.469529

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記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Rotational spectra of carbon-chain molecules C5O, C7O, and C9O have been observed for the first time by using a Fabry-Perot type Fourier transform microwave (FTMW) spectrometer cooperated with a pulsed discharge nozzle (PDN). The molecules have been generated by the discharge of C3O2 diluted in Ar. The spectra consist of series of R-branch transitions typical of linear molecules in singlet electronic states. For C5O, transitions for all the possible singly substituted C-13 and O-18 isotope species have also been detected in natural abundance. These measurements with an assumption of linearity have enabled a complete substitution structure to be derived: r(s)(C-(1)-O) = 1.1562(11) Angstrom, r(s)(C-(2)-C-(1)) 1.2552(30) Angstrom, r(s)(C-(3)-C-(2)) = 1.2881(38) Angstrom, r(s)(C-(4)-C-(3)) = 1.2947(21) Angstrom, and r(s)(C-(5)-C-(4)) = 1.2736(10) Angstrom. The CC bond lengths in C5O were found to be much more uniform than those in an isoelectronic molecule HC5N. The canonical structure which reproduces observed internuclear distances in C5O has been suggested. By assuming the same partial structure as that in the C5O molecule, the averaged bond lengths for the rest of C-C bonds in C7O and C9O have been determined to be 1.270 and 1.274 Angstrom, respectively. Along with the recent results of tripler CnO (n = 2, 4, 6, and 8) [Ohshima, Endo, and Ogata, J. Chem. Phys. 1995, 102, 1493-1500], the CC bonds in CnO are found to become more uniform cumulene-type double bonds with increasing n and to converge to a constant length.

DOI： 10.1021/ja00117a027

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記述言語：英語  

DOI： 10.1063/1.469529

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

DOI： 10.1063/1.468881

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DOI： 10.1006/jmsp.1995.1170

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

A new carbon-chain free radical, HC4O, has been identified in the gas phase through its rotational spectrum. The molecule has been generated in a supersonic free jet by electric discharge of an acetylene/oxygen mixture diluted in Ar, and detected by a Fabry-Perot type Fourier-transform microwave spectrometer. Four harmonically related rotational transitions have been observed in the 9-23 GHz region. They all showed fine structure splittings accompanied with well resolved hyperfine structures due to the hydrogen nucleus. Observation of other isotopomers, DC4O and (HC4O)-O-18, has yielded confirmation for the molecular species. The observed spectra have been well characterized as K-a = 0 transitions of a slightly asymmetric top molecule in a doubler vibronic state. The effective centrifugal distortion constant has been found to be fairly large, implying that the molecule has a bent carbon-chain framework. The present observation indicates that the radical is subjected to a strong (i.e., static) Renner-Teller interaction, resulting in a complete quenching of the orbital angular momentum in a nonlinear molecular structure as is the case of shorter members of the HC,O series. The isotropic hyperfine coupling constant shows that almost half of the unpaired electron lies on the carbon atom adjacent to the hydrogen.

DOI： 10.1063/1.468370

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DOI： 10.1063/1.468292

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DOI： 10.1063/1.468292

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記述言語：英語   出版者・発行元：ROYAL SOC CHEMISTRY  

Pure rotational spectra of a few Van der Waals complexes containing short-lived species have been observed in our laboratory. They are produced in a supersonic jet by using a pulsed-discharge-nozzle (PDN) system combined with a Balle-Flygare Fabry-Perot type Fourier-transform microwave (FTMW) spectrometer. Among the species so far observed, detailed analysis of Ar-OH is presented in this paper. This complex has unquenched orbital and electron-spin angular momenta, which couple with the large amplitude motion of the complex. Fine and hyperfine structures observed in the present study have been analysed on the basis of an internal-rotation model for the OH monomer hindered by a small anisotropic intermolecular potential.

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

Vibration-rotation transitions of the C2H2-Ar complex have been observed in the doubly degenerate monomer C-H bending (nu5) region via direct IR absorption of tunable diode laser radiation in a pulsed supersonic free jet. The spectrum is composed of in-plane and out-of-plane C-H bending bands, which are coupled with each other through a strong Coriolis interaction. Anomalous Coriolis coupling and A rotational constants indicates the failure in a semirigid-molecule description of this highly nonrigid system in the doubly degenerate bending manifold. A dynamical model calculation, where the large-amplitude van der Waals bending motion is treated as an internal rotation of the C2H2 monomer hindered by an anisotropic intermolecular potential, has revealed that the characteristic energy-level structure originates from its specific angular momentum coupling scheme involving an additional angular momentum for the intramolecular degenerate bending. The difference potential providing the parity doubling in the C-H bending manifold is estimated to be only about -0.1 cm-1.

DOI： 10.1063/1.465614

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記述言語：英語  

The rotational spectrum of 24Mg35Cl in its X 2Σ+ (ν=0 and 1 ) state has been observed in the 14 GHz region by using a Fourier- transform microwave spectrometer combined with a laser-ablation source. The radical was produced by the reaction of atomic Mg vaporized by 532 nm laser light with Cl2 diluted in Ar. The present observation of the lowest N transition by a high-resolving power instrument has provided accurate hyperfine coupling constants associated with the 35Cl nucleus of this molecule. © 1993.

DOI： 10.1016/0009-2614(93)85424-M

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記述言語：英語   出版者・発行元：ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS  

DOI： 10.1006/jmsp.1993.1142

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

Two low-J transitions, N(J) = 1(0)-0(1) and 1(2)-0(1), of the HCCN radical in its 3SIGMA- ground state have been studied by a pulsed-discharge-nozzle Fourier-transform microwave spectrometer. Spectrum with well-resolved hyperfine splittings due to hydrogen and nitrogen nuclei was observed, which enabled us to determine accurate hyperfine coupling constants for both the nuclei for the first time in the present study, as well as a much improved spin-spin coupling constant. These hyperfine coupling constants suggest that the electronic structure of the HCCN radical can be described as the one with the allenic structure to be almost twice more important than the carbenic structure. The present results seems to support a conclusion that the molecular structure of the radical is almost linear with a possibility of a large amplitude bending motion.

DOI： 10.1063/1.464804

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記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Pure rotational spectra and their Stark effects Of X-CO2 type complexes (X: Ne, Kr, and Xe) have been studied by pulsed-nozzle Fourier-transform microwave spectroscopy. Structures, intermolecular force fields, and electric dipole moments in the ground state have been determined, which have been discussed in connection with the previously reported results of Ar-CO2 and Hg-CO2. When the polarizability of the attached atom is small, the dipole moment has been well reproduced by a two-center expansion model for the induction interaction, where the atom is polarized by the electric field arising from the quadrupole moment Of CO2. However, this simple model deviates systematically as the atoms possess larger polarizabilities, implying a finite size effect of the attached atom. A model calculation to describe intermolecular potential functions has been performed to show that the vdW force constants of X-CO2 have been mainly controlled by the repulsion and dispersion interactions.

DOI： 10.1021/j100104a016

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記述言語：英語   出版者・発行元：ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS  

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記述言語：英語   掲載種別：速報，短報，研究ノート等（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

DOI： 10.1063/1.461806

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

The pure rotational spectrum of the benzene-N-15(2) complex has been observed by a pulsed-nozzle Fourier-transform microwave spectrometer. The observed spectrum consists of two internal-rotation states and evidently shows the existence of an almost-free rotational motion of N2 within the complex. The rotational and centrifugal-distortion constants for the ground internal-rotation state have been determined precisely. An analysis of the centrifugal-distortion constants has been carried out to derive information on the intermolecular vibrations.

DOI： 10.1016/0009-2614(91)87158-8

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

DOI： 10.1063/1.458995

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記述言語：英語   掲載種別：記事・総説・解説・論説等（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

DOI： 10.1063/1.457810

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DOI： 10.1016/S0009-2614(90)87169-R

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DOI： 10.1063/1.458076

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DOI： 10.1016/S0009-2614(90)87169-R

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DOI： 10.1063/1.458076

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

DOI： 10.1063/1.454419

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

DOI： 10.1016/0009-2614(88)80213-6

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記述言語：英語  

DOI： 10.1016/0009-2614(88)80213-6

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

DOI： 10.1063/1.453682

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記述言語：英語  

DOI： 10.1063/1.453682

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