Yoshihiro Yamakita

Yoshihiro Yamakita
University of Electro-Communications | UEC · Department of Engineering Science

D.Sc

About

35
Publications
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932
Citations

Publications

Publications (35)
Article
The electronic structures of chalcogenoanisole C6H5XCH3 (X = O, S, and Se) have been determined by Penning ionization electron spectroscopy experiments with density functional theory (DFT), multi-configuration molecular orbital, and natural bond orbital (NBO) calculations. Ionization energies and electron distributions outside molecular surfaces we...
Article
The reaction dynamics of Penning ionisation of a polycyclic aromatic hydrocarbon (PAH), naphthalene C10H8, in collision with the metastable He*(2³S) atom is studied by classical trajectory calculations using an approximate interaction potential energy surface between He* and the molecule, which is constructed based on ab initio calculations for the...
Article
Femtosecond ultrafast electronic relaxation and vibrational dynamics in 2’-hydroxychalcone after deep ultraviolet (DUV) excitation were observed by two types of pump-probe spectroscopy experiments, i.e., DUV-pump pulse and visible-broadband-probe pulse (DUV/Vis) experiments and DUV-pump and DUV-probe (DUV/DUV) pulses experiments. Time-dependent den...
Conference Paper
This paper reports on a highly-sensitive retarding-type electron spectrometer for a continuous source of electrons, in which the electron collection efficiency is increased by utilizing the magnetic bottle effect. This study demonstrates an application to Penning ionizationelectron spectroscopy using collisional ionization with metastable He*(2³S)...
Article
The velocity and angular distributions of Mg+(2P3/2) produced by photolysis of Mg+-Ar complex at 4.66 eV were observed using an apparatus set up for imaging fragment ions from mass-selected ions. The translational energy Et and the anisotropy parameter β were measured to be 640 ± 80 cm−1 and 1.03 ± 0.05, respectively. The binding energy of Mg+-Ar i...
Article
Full-text available
The phonon dispersion curves are presented for a carbon nanoribbon, polyacene. Restricted and unrestricted density functional calculations for [n]oligoacenes (n = 10 and 15) predict different spin distributions in the singlet electronic state. The unrestricted states involve spin-localized, singly-occupied orbitals. Bond alternations, infrared acti...
Article
Conformationally dependent ionization of the simplest amino acid, glycine, is studied by Penning ionization electron spectroscopy with velocity-resolved metastable He*(2(3)S) atoms. The observed He I ultraviolet photoelectron and Penning ionization electron spectra are reproduced by superimposed theoretical spectra, assuming thermal distributions o...
Article
Penning ionization electron spectra (PIES) of pyrene (C(16)H(10)), chrysene (C(18)H(12)), and coronene (C(24)H(12)) in the gas phase are recorded using metastable He(*)(2 (3)S) atoms. The assignments of PIES are presented based on the outer valence Green's function calculations with the correlation consistent polarized valence triple-zeta basis set...
Article
Nonresonant Raman spectra and conformational stability are studied for thioanisole (TA) and substituted analogues [4-XTA, X = NO(2) (1), CN (2), H (3), CH(3) (4), and NH(2) (5)] at the 4-position. The ring-substituent (SCH(3)) vibrational modes of out-of-plane bending and torsional types are calculated to have strong Raman scattering activities onl...
Article
Phonon dispersion relations are presented for carbon nanoribbons along multirow structures of hexagonal rings with zigzag and armchair edges. The dispersions are compared with the ΓK and ΓM dispersions of graphite as a function of ribbon width m. The force constants are obtained from zone folding for those of polycyclic aromatic hydrocarbons (PAHs)...
Article
This paper presents calculations for realizing the deceleration of H2 Rydberg molecules with n = 16, where n is the principal quantum number. A double-dipole decelerator (Softley T P, Procter S R, Yamakita Y, Maguire G and Merkt F 2005 J. Elec. Spectrosc. Relat. Phenom. 144–147 113) operated with an optimum time-dependent electric field allows, in...
Article
Full-text available
As model compounds for nanosize carbon clusters, the phonon dispersion curves of polyacene are constructed based on density functional theory calculations for [n]oligoacenes (n=2-5, 10, and 15). Complete vibrational assignments are given for the observed Fourier-transform infrared and Raman spectra of [n]oligoacenes (n=2-5). Raman intensity distrib...
Article
The large nonresonant Raman-scattering activities of the out-of-plane bending and torsional modes of monosubstituted benzene analogs are studied by low-frequency Raman experiments and B3LYP6-31++G(d,p) calculations. Electronic interactions between the sigma orbitals of the substituent and the pi orbitals of the ring are found to enhance the Raman a...
Article
Full-text available
The DC Stark effect is studied for high Rydberg states (principal quantum number n ≥ 15) of helium atoms in the triplet spin state. A signal is detected through pulsed field ionization by an electric field F = 6000V/cm with a slew rate of 4.0 ×10 10 Vcm −1 s −1 . Stark manifolds are clearly observed in the region below the classical saddle point en...
Article
Hydrogen molecules are excited by 1 + 1′ (VUV + UV) laser excitation to Rydberg states (n = 15–20) in the inhomogeneous field generated by an electrostatic dipole. High-field or low-field seeking Stark states are selected spectroscopically and experience a force either towards or away from the dipole, respectively. Deflection of the molecular beam...
Article
Hydrogen molecules are excited in a molecular beam to Rydberg states around n=17-18 and are exposed to the inhomogeneous electric field of an electric dipole. The large dipole moment produced in the selected Stark eigenstates leads to strong forces on the H2 molecules in the inhomogeneous electric field. The trajectories of the molecules are monito...
Article
The deflection and deceleration of neutral hydrogen molecules in the presence of an inhomogeneous electric field is demonstrated. The molecules are laser-excited in a molecular beam to selected Rydberg–Stark states in the field of an electric dipole for a fixed period, and their trajectories are monitored using ion imaging and time-of-flight measur...
Article
The dissociative excitation of BrCN producing CN(B2Σ+) fragment by the collision of He*(23S) was investigated by the collision energy-resolved electron and emission spectroscopy using time-of-flight method with a high-intensity He* beam. The Penning electrons ejected from BrCN and the subsequent CN(B2Σ+–X2Σ+) emission were measured as a function of...
Article
Non-resonant Raman intensities for alkylbenzenes were studied based on FT-Raman spectra and density functional calculations. Strong bands were found for a bending mode and a torsion mode in a range of , where no strong bands were observed for benzene and alkanes. In a staggered form of ethylbenzene and a gauche form of n-propylbenzene, non-totally...
Article
A magnetic bottle electron spectrometer with retarding electrodes has been applied to observation of Penning ionization electron spectra (PIES) of van der Waals clusters. Considerably increased efficiency of the spectrometer by 1000 times over the conventional PIES apparatus enabled us to measure electron spectra of van der Waals clusters of rare g...
Article
Penning ionization electron spectra (PIES) of CO2 clusters have been observed for the first time. An unusually fast electron band with excess kinetic energies of 1.4–2.9 eV with respect to the monomer band for the ionic X state was observed for CO2 clusters in collision with He*(23S) atoms. While for PIES with Ne*(33P), no such unusual band was obs...
Article
Full-text available
A highly sensitive electron energy analyzer which utilizes a “magnetic bottle” combined with a retarding electrostatic field has been developed for Penning ionization electron spectroscopy. A beam of metastable rare-gas atoms is crossed with a continuous supersonic sample beam in the source region of the analyzer. The emitted electrons are collecte...
Article
Penning ionization of [2,2]-paracyclophane (PC) with metastable He*() atoms has been studied by means of simultaneous detection of collision energy and electron energy. Negative collision energy dependences of partial Penning ionization cross-sections have been observed in the range of 115–283 meV. This indicates the presence of an attractive poten...
Article
Penning ionization electron spectra (PIES) of van der Waals clusters have been observed for the first time by means of a newly developed magnetic bottle electron spectrometer, which is 1000 times more efficient than a conventional PIES apparatus. In the PIES of Ar clusters with He∗(2 3S), two bands of Ar 3p hole characters with different ionization...
Article
Ionization threshold energies of clusters of Li and Na atoms solvated by acetone have been determined by laser photoionization. The thresholds for 1:1 complexes agree well with calculated adiabatic ionization potentials based on density functional theory. The structures and charge distributions obtained from the calculation show that electron trans...
Article
Full-text available
Negative ions of copper clusters reacted with nitric oxide molecules are studied by mass-selected photoelectron spectroscopy. The series of the reacted cluster ions, Cun N-, Cun NO-, and Cun NO2- are observed in the mass spectrum. Photoelectron spectra are obtained at 3.49 eV photon energy for Cun N- (n=2 and 3) and Cun NO2- (n=1 and 2). The photoe...
Article
Photoionization mass spectroscopy of clusters of alkali metal atoms solvated with acetonitrile molecules, M(CH3CN)n (M=Li and Na), has shown that their ionization potentials decrease from n=1 to 3, while they increase for n⩾4. Calculations based on density functional theory are also made for these clusters and their cations with n=1–3. The nature o...
Article
Penning ionization of naphthalene and anthracene with He*(2(3)S) atoms has been studied by means of simultaneous detection of collision energy and electron energy. The anisotropy of interaction potentials between He*(2(3)S) atoms and the target molecules has been found on the basis of the collision energy dependences of partial Penning ionization c...
Article
Theoretical calculations of Raman spectra have been performed for naphthalene, anthracene, pyrene, and perylene. Normalcoordinate calculations have been carried out by ab initio Hartree-Fock (HF) theory, density functional (DF) theory, and a simple force field model ( model). Raman intensities have been evaluated for each normal coordinate by the f...
Article
An extensive analysis of the infrared and Raman spectra of p-benzoquinodimethane (p-BQM) has been performed, based on a reanalysis of the vibrational spectra of p-benzoquinone (p-BQ). Optimizations of structure parameters have been carried out at the Hartree-Fock and the second-order Moller-Plesset perturbation levels. Force constants in the Cartes...
Article
Electronic structures in metallic and insulating phases of the Li, Cu, and Ba complexes of 2,5-R1,R2-DCNQI [R1=R2=Br (abbreviated as DBr) or R1=R2=CH3 (abbreviated as DMe); DCNQI=N,N’-dicyanoquinonediimine; 2,5- is usually omitted] have been studied by observing temperature dependencies of their infrared absorption bands between 295 and 23 K. At ro...
Article
The unique molecular conductors with ppi-d mixing band structures (R1,R2-N,N'-dicyanoquinonediimine)2Cu [(R1,R2-DCNQI)2Cu] (R1,R2=CH3,CH3O,Cl,Br) were examined. General features of the phase diagram of the DCNQI-Cu system were depicted. A region that is related to the existence of anomalously heavy-metal electrons has been found. The T2 dependence...
Article
The infrared and Raman spectra of p-benzoquinodimethane have been observed in low-temperature Ar matrices. The infrared spectrum obtained has proved to be more reliable and useful than the existing numerical data on the absorption wavenumbers and qualitative intensities. The Raman spectrum has been observed for the first time. Vibrational assignmen...
Article
Full-text available
The Stark effect is studied for the gerade Rydberg states (principal quantum number n ≥ 16) of molecular hydrogen by using vacuum ultraviolet/ultraviolet two-photon excitation and detecting ions produced by de- layed field ionization. Experiment and theory show that the nd Rydberg states with N + = 2, J = 1, MJ = 0 are long-lived, and have predomin...

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