Y. Morioka

Raman depolarization ratios of jet-cooled benzene and its dimer by stimulated Raman—UV optical double-resonance spectroscopy

Abstract By the use of double resonance of stimulated Raman pumping and mass-selected resonance enhanced multiphoton ionization, the depolarization ratios of the Raman bands of jet-cooled benzene and its dimer have been measured for the first time. The depolarization ratio of the totally symmetric ring breathing vibration (mode 1) showed a drastic change upon dimer formation. We found two kinds of dimer which give different depolarization ratios of ϱ = 0.1 and 0.02. By applying the model proposed by Hyodo and Fujiyama, the dimers of ϱ = 0.1 and 0.02 were concluded to be those having different intermolecular distances of 3.6 and 5 A, respectively.

Crystallochemical Studies on the High Temperature Superconductors La2-xMxCuO4-y (M=Ba and Sr)

High temperature superconductors La2-xMxCuO4-y (M=Ba and Sr) with the K2NiF4 structure were synthesized by solid state reaction and characterized by X-ray diffraction, electron microscopy, IR measurements and thermogravimetry. Anomalous behavior of unit cell parameters was confirmed. Electron diffraction study of the orthorhombic La2CuO4 revealed weak forbidden spots for Fmmm symmetry, suggesting a space group of lower symmetry. One of three IR bands observed in La2CuO4 rapidly disappeared around x=0.1. Highest superconducting transition temperature was found to be 38.0 K in La1.85Sr0.15CuO3.96.

Optical activity in the metastable state of Na2[Fe(CN)5NO].2H2O crystals

Abstract The Na 2 [Fe(CN) 5 NO]·2H 2 O crystal is transformed into its metastable state when it is irradiated with blue or green laser light at low temperatures below 160K. This work describes newly found anomalous optical properties in the metastable state. Under the observation with white light illumination and crossed polarizers, a bright color is visible due to the incomplete extinction. The spectrum of this color has a rather narrow band-width of about 15nm. The wavelength of the maximum intensity, λ MAX , shifts with the wavelength of the irradiated laser light, but is not affected by the thickness of the sample. The incomplete extinction at a narrow range of wavelengths can be explained in terms of the optical activity and the accidental coincidence of two principal indices of refraction at λ MAX . This suggests that the optical activity arises in the metastable state.

Raman spectra of YBa2Cu3-xMxOy(M=Co, Ni) superconductors

Abstract Raman spectra of tetragonal YBa 2 Cu 3−x Co x O y which contains oxygen disorder as well as orthorhombic YBa 2 Cu 3 O y and YBa 2 Cu 3−x Ni x O 7 were recorded. With Co doping, a broad band appears at 573 cm −1 , the 500 cm −1 band of orthorhombic YBa 2 Cu 3 O y decreases in frequency, and the 115 cm −1 band disappears. The origin of the 573 cm −1 band can be attributed to the infrared active Cu-O stretching mode which becomes Raman active due to the oxygen disorder. The latter two indications are the same as those in the case of oxygen deficient tetragonal phase. Mode patterns of observed Raman bands of orthorhombic YBa 2 Cu 3 O y are also discussed.

Hyper-Raman spectra of some cubic crystals

Abstract Hyper-Raman spectra of SrTiO 3 , CsCaCl 3 , CsI and NaCl were observed by a 1.06 μm line from an acousto-optically Q -switched Nd: YAG laser and a multichannel detection system. The TO and LO frequencies of CsCaCl 3 are slightly different from those obtained by the far-infrared reflection spectrum.

Far-infrared studies of alkali-anthracene ion-pairs and triple-ions in solution

Abstract Solutions of the anthracene mono- and di-anion produced by reduction with alkali metals in tetrahydrofuran show absorption bands in the far-infrared region. These bands have been interpreted as arising from the vibration of ion-pairs and triple-ions. The corresponding force constants have been calculated using simple models. Some discussions is given of possible causes of the two absorption bands of the sodium-anthracene triple-ion.

Far-infrared spectra of alkali naphthalene ion pairs in solution

Abstract The far-infrared spectrum of an ethereal solution of the naphthalene radical anion prepared by reduction with an alkali metal shows an absorption band which is considered to be due to a vibration of an ion pair. The corresponding force constant was calculated for each ion pair from the observed frequency. The obtained values are of reasonable magnitude.

Raman spectroscopic and optical study on the light-induced metastable state of Na2[Fe(CN)5NO]·2H2O single crystal

Abstract A light-induced metastable state of a Na 2 [Fe(CN) 5 NO]·2H 2 O single crystal was studied by using Raman spectroscopy and optical transmission measurements. Intramolecular vibrations of the metastable molecule have been unambiguously identified from the polarized Raman measurement. Lattice vibrations were not affected significantly by the formation of the metastable state, indicating that the change in the crystal structure is small in the metastable state. Strong elastic light scattering was observed in the course of the formation of metastable state. This phenomenon is attributed to the optical inhomegeneity of the crystal arising from the domain structure of the metastable state.

Kinetic analysis of superconducting YBa2O7, by thermogravimetry in high vacuum

Abstract Superconducting YBa 2 Cu 3 O 7 , was subjected to high vacuum thermogravimetry (TG) at various heating rates in the range from room temperature to 1000°C. Two distinct weight-loss steps, each of which corresponds to the evolution of almost 1/20 2 , were observed on the TG curve. The product following the first step was apparently the non-stoichiometric compound YBa 2 Cu 3 O 7-δ . The rate equation for the first step was dδ/d t = k (1-δ); the corresponding specific rate constant, k , was 1.8 × 10 −3 s −1 at 490°C, the activation energy, E a , was 75 kJ mol −1 and the frequency factor, A , was 3.0 × 10 2 s −1 .

Raman spectra of YBa2Cu3Ox(x=6−7)

Abstract Raman spectra of polycrystalline YBa 2 Cu 3 O x with various oxygen content x were recorded at 30 K. The intensity of the Cu-O stretching mode at 505 cm -1 depends on the oxygen content significantly. This peak becomes weak as the oxygen content decreases and finally disappears at x =6.05. The last result disagrees with previous Raman studies on the tetragonal phase. Other spectral changes, disappearance of the 115 cm -1 peak and shifts of some peaks, are observed at the oxygen content of ≈6.8.