Yasuo Udagawa

Resonance Raman effect of I−3 ion by ultraviolet laser excitation

Abstract The resonance Raman effect of the I −1 3 ion was observed by the use of an ultraviolet nitrogen pulsed laser. It was found that the totally symmetric stretching vibration of 112 cm −1 undergoes selective enhancement and the overtones up to the seventh order of this vibration could be observed. The result agrees well with the prediction by Nafie et al.

Optical spectra of liquid water in vacuum uv region by means of inelastic x-ray scattering spectroscopy

Inelastic x-ray scattering (IXS) spectroscopy using hard x-rays is in principle equivalent to optical spectroscopy as long as momentum transfer can be approximated to be zero. Hence IXS spectra of liquid water which corresponds to vacuum uv absorption were measured at small energy transfers with energy resolution of 0.5 eV. The loss function was derived from the spectra and its convergence for the momentum transfer smaller than 0.28 a.u. was confirmed. The reflectance spectrum and the optical oscillator strength have been calculated from the loss function. It is shown that the optical oscillator strength of liquid water differs considerably from that of gaseous water.

Single vibronic level fluorescence from n, π* state of pyrazine vapor

Abstract Fluorescence spectra from various single vibronic levels of the 1 B 3u state of pyrazine- h 4 and — d 4 vapors have been observed and analyzed, leading to unambigous assignments of a number of absorption bands. Nine excited state fundamentals have been established for pyrazine- h 4 . Ground state fundamentals of b 2g and a u species have been confirmed as well. From the observations of anharmonic couplings between the vibrations belonging to different symmetry in D 2h point group, lowering of molecular symmetry in 1 B 3u state has been suggested.

Channel-three decay in benzene a picosecond fluorescence investigation

Abstract Fluorescence quantum yields, decay times and spectra have been measured following excitation of benzene vapour above the channel-three threshold. Experiments have been carried out on the static gas and on molecules jet-cooled to a vibrational temperature of 160 K. The excitation source was a recently developed high-power, picosecond, narrow-bandwidth laser continuously tunable from 224 to 252 nm. Channel-three decay was observed for all vibrational levels, even those not excited via line-broadened transitions. In addition it was observed that fluorescence decay curves resulting from excitation just above the channel-three threshold were non-exponential. It is proposed that the cause of absorption line broadening — intramolecular vibrational redistribution — is not directly related to channel-three, which is postulated to be coupling to a state X , which could be an isomeric form of benzene or a hidden singlet electronic state.

Characterization of iron oxide in Fe2O3/SiO2 catalyst

Abstract Silica-supported iron oxide catalyst was prepared by hydrolysis of a mixed solution of ethyl silicate and iron(III) nitrate dissolved in ethylene glycol. A gel obtained by the hydrolysis was dried and calcined at various temperatures. The iron oxide particles thus prepared were maghemite (γ-Fe2O3), deduced by EXAFS (extended X-ray absorption fine structure) measurements and the sample color. The maghemite particles were classified into two groups: one is small but detectable by transmission electron microscopy (TEM) and the other is too small to be detected by TEM. The former was well controlled to a consistent size, which depended on the calcination temperature, and exhibited ferrimagnetic properties. The latter showed superparamagnetic properties and was estimated to be smaller than 10 A in particle size by magnetic and Mossbauer measurements at low temperature. For comparison, the catalyst was also prepared by a conventional impregnation method using silica powder and an aqueous solution of iron(III) nitrate. Iron oxide thus prepared was hematite (α-Fe2O3) and the particle sizes were broadly distributed.

Raman spectra of pyrazine resonant to the S2(π,π*) state and the geometry in excited state

Abstract Raman spectra resonant to the S 2 (π,π * ) state of pyrazine vapor consist of fundamentals, overtones and combinations of only two totally symmetric vibrations, ν 1 and ν 6a . Combining the Raman with the absorption spectra it is experimentally verified that the molecules deformation upon excitation is reflected on the resonance Raman spectra.

Vibronic coupling and Raman intensities of pyrazine

Abstract The fluorescence spectrum of pyrazine vapour and the Raman spectra of liquid pyrazine excited at various wavelengths were observed. The appearance of the long progression of the hydrogen bending vibration ν 5 (b 2g ) in the fluorescence spectrum and a remarkable preresonance effect of the Raman line of the same vibration confirm the theoretical prediction given by Albrecht.

Theoretical fine spectroscopy with symmetry-adapted-cluster configuration-interaction method: Outer- and inner-valence ionization spectra of furan, pyrrole, and thiophene

Theoretical fine spectroscopy has been performed for the valence ionization spectra of furan, pyrrole, and thiophene with the symmetry-adapted-cluster configuration-interaction general-R method. The present method described that the pi(1) state interacts with the pi(3) (-2)pi*, pi(2) (-2)pi*, and pi(2) (-1)pi(3) (-1)pi* shake-up states providing the split peaks and the outer-valence satellites, both of which are in agreement with the experiments. The intensity distributions were analyzed in detail for the inner-valence region. In particular, for furan, theoretical intensities were successfully compared with the intensity measured by the electron momentum spectroscopy. The interactions of the 3b(2) and 5a(1) states with the shake-up states were remarkable for furan and pyrrole, while the 4b(2) state of thiophene had relatively large intensity.

Laboratory EXAFS spectrometer with a bent crystal, a solid‐state detector, and a fast detection system

A laboratory x‐ray absorption spectrometer is described which consists of a Johansson‐cut bent crystal, a rotating anode x‐ray generator, and a fast SSD (solid‐state detector). Because the SSD can completely discriminate the undesired reflections, contamination of the harmonics is avoided while maintaining a high‐source voltage necessary for strong x‐ray flux. Fast electronics equipment is employed to keep up with high‐x‐ray intensity. It is also possible to utilize higher‐order reflections for high resolving power. The data of quality comparable to those obtained at synchrotron radiation facilities can be obtained in a comparable period of time. In addition, the determination of the absolute absorbance as defined is possible, which makes the problem of the background subtraction in EXAFS analysis easy.

Raman spectra and Jahn-teller effects of C4O2-4 and C5O2-5 ions

Abstract The Raman spectra of highly symmetrical ions C 4 O 2- 4 (D 4h ) and C 5 O 2- 5 (D 5h ) have been measured at various excitation wavelengths. The spectra are characterized by strong Raman intensities of some non-totally symmetric vibrations at off-resonant condition and their remarkable intensity enhancement at near and rigorous resonant conditions. The characteristic features of the Raman spectra are closely related with the Jahn-Teller effects of the lowest degenerate π,π* electronic excited states of these ions.