Yoshiyuki Morioka

Vibrational spectroscopic study of light-induced metastable states of ethylenediaminenitrosylruthenium(II) complexes

Abstract Light-induced metastable states were found in trans - and cis -[RuCl(en) 2 NO]Cl 2 , trans - and cis -[RuBr(en) 2 NO]Br 2 , trans -[Ru(H 2 O)(en) 2 NO]Cl 3 , and a mixture of fac - and mer -[RuCl 3 (en)NO]. These states are formed when the polycrystalline samples are irradiated with blue or green laser lines from an Ar ion laser at 77 K. They decay upon irradiation with red light or a rise in temperature. The NO stretching frequency that is observed in the range from 1865 to 1904 cm −1 in the ground (normal) state of each compound shifts to the lower frequency side by approx. 100–140 cm −1 in the metastable states. These characteristics are similar to those of the metastable states of Na 2 [Fe(CN) 5 NO]·2H 2 O, K 2 [RuHCl 5 NO] and K 2 [Ru(NO 2 ) 4 (OH(NO)]. Decay temperatures of the ethylenediaminenitrosyl-ruthenium(II) complexes are notably higher (approx. 230–270 K) than those of the substances examined in earlier studies (approx. 180–190 K).

Raman Scattering from High-Tc Superconductor YBa2Cu3O7-x and Its Analogs

Raman spectra of polycrystalline samples of orthorhombic YBa2Cu3O7-x, HoBa2Cu3O7-x, NdBa2Cu3O7-x, metastable tetragonal YBa2Cu3O7-x, and Y2BaCuO5 were measured at room temperature. Spectral differences among these materials were clarified and tentative assignments of the observed bands to the Raman active lattice vibrations were proposed.

Raman and Infrared Spectra and Lattice Vibrations of KNO3 Crystal

Polarized Raman and infrared reflection spectra of KNO 3 crystals have been measured at room temperature. Raman and infrared transmission spectra of the high temperature phase of KNO 3 have been also measured. The frequencies of the transverse (TO) and longitudinal (LO) modes of the infrared active vibrations of the crystal have been obtained from the observed reflectivities. The lattice dynamical analysis of the optical active vibrations of the room temperature phase of KNO 3 has been made based on a rigid ion model which includes effective ionic charges and short-range repulsive force constants. Short-range force constants for the non-bonded metal-oxygen and oxygen-oxygen interactions have been determined by the least squares method using the observed Raman frequencies.

Molecular vibrations and structure of the light-induced metastable state of [Fe(CN)5NO]2−

Abstract The molecular structure of the metastable state (MS1) of sodium nitroprusside was studied by polarized Raman spectroscopy and the normal coordinate analysis on 14 NO - and 15 NO -substituted crystals. The downshift of the bending mode of the Fe–(NO) bond upon 15 NO substitution is significantly smaller in MS1 than in the ground state. The normal coordinate analysis indicates that the effect of the N-atom mass on the mode is large in the Fe–N–O linkage but small in the Fe–O–N linkage. The small isotope shift observed in MS1 suggests the Fe–O–N linkage that was proposed in a recent X-ray diffraction study.

Hyper-Raman Study of Ferroelectric Phase Transition of Li2Ge7O15

The ferroelectric phase transition of Li 2 Ge 7 O 15 was investigated by means of the hyper-Raman scattering. The under damped soft mode was observed at temperatures above 305 K in the paraelectric phase. In the further lower temperature region, an unresolved central peak is observed. The temperature dependence of the intensity of the central peak is characterized by the diverging behavior near the transition temperature and the linear increase with decreased temperature in the ferroelectric phase. These can be attributed to the hyper-Raman scattering due to the polarization fluctuation, and the optical second harmonic generation which becomes active in the ferroelectric phase, respectively.

Raman Study of Structural Phase Transition in K3Co(CN)6

Raman spectra of K 3 Co(CN) 6 crystals have been observed at temperatures down to 30 K. The lowest frequency band in the low temperature phase, ∼13 cm -1 at 30 K, softens to 5 cm -1 near the transition temperature (∼63 K). This soft mode behavior shows that the phase transition is displacive one. Since no soft optically active modes arc found in the high temperature phase, the instability of the high temperature lattice is ascribed to the zone boundary phonon.

Crystal Structures of the Room- and Low-Temperature Phases of Monoclinic Potassium Ferricyanide

Crystals of K 3 Fe(CN) 6 undergo a second-order phase transition accompanied by a soft mode at about 130 K. The crystal structures of the room- and low-temperature phases have been determined by X-ray diffraction. Crystals of the room-temperature phase are monoclinic with space group P 2 1 / c , a =7.058(1), b =10.426(1), c =8.401(1) A, β=107.31(1)° and Z =2 at 293 K. Those of the low-temperature phase are monoclinic with space group P 2 1 / n , a =14.021(2), b =10.401(1), c =8.339(2) A, β=107.21(1)° and Z =4 at 100 K. Final R values were 0.029 for 1591 observed reflections and 0.027 for 2642 observed reflections for the room- and low-temperature phases respectively. With a transition from room- to low-temperature phase, [Fe(CN) 6 ] 3- anions displace by about 0.1 A along the b axis. A soft mode is considered to be a translational lattice mode of [Fe(CN) 6 ] 3- anions which has a wave vector a * /2 in the room-temperature phase.

Raman Scattering and Phase Transitions in BaZnGeO4 Crystal

The polarized Raman spectra of BaZnGeO 4 crystal were measured at various geometrical arrangements corresponding to A(TO), E 1 (TO)+E 1 (LO) and E 2 representations over the temperature range 440°C∼-110°C, which covers the whole phases except for the phase I. In the low-frequency region below 300 cm -1 , the spectral feature varies depending upon temperature and a characteristic pattern of Raman spectrum for each phase is clarified. The spectral change due to the II-III phase transition appears continuous, in agreement with the second order nature. No spectral change is observed in the III-IV transition. The phase transition IV-V is clearly distinguished in the Raman spectra by an abrupt change of several bands and a thermal hysteresis, which reflects the first order nature.

Far infrared and Raman spectra, and lattice vibrations of K2Zn(CN)4, K2Cd(CN)4 and K2Hg(CN)4

Abstract Infrared and Raman spectra of K 2 M(CN) 4 (M: Zn, Cd and Hg) have been measured down to 10 cm −1 . For K 2 Zn(CN) 4 a measurement of polarized Raman spectra of single crystals has been made. Observed infrared and Raman spectra bands arising from both inner vibrations in the complex ion and lattice vibrations have been assigned to each species on the basis of the factor group analysis. A normal coordinate analysis of the optical active crystal vibrations has been performed, the interatomic force constants between the atom pairs whose distances are shorter than 4·0 A being taken into account and the long-range electrostatic interactions being neglected. The metal—ligand force constants K(MC) obtained vary in the order Hg > Zn ≈ Cd. The nature of each lattice vibrations as well as each inner vibration has been clarified for this series of complex salts.

AgI-intercalation into Bi2Sr2CaCu2Oz compound

Abstract Polycrystalline AgI-intercalated Bi 2 Sr 2 CaCu 2 O z is prepared and the structure and physical properties studied. The lattice parameters a and c are determined to be 5.40 and 22.8 A, respectively. The expansion of the lattice parameter c is 7.4 A, compared with that of a Bi 2 Sr 2 CaCu 2 O z (Bi2212) specimen ( c/2: 15.4 A ). This expansion is more than twice as large as that of iodine-intercalation (3.6 A). The EPMA measurement shows that the I/Ag ratio in the AgI-intercalated specimen is greater than 1.0. The T c is 69 K, which is lower than that of Bi2212 (75 K) and almost the same as that of IBi 2 Sr 2 CaCu 2 O z (IBi2212, 67 K). The effect of AgI-intercalation on the superconductivity is discussed.