Yoshiyuki Matsumoto

Raman Scattering Study of (NH 4) 3H(SeO 4) 2 Single Crystal in High Temperature Phases

Raman scattering from a single crystal of Rb 3 H(SeO 4 ) 2 has been observed in the frequency range between 20 cm -1 and 1000 cm -1 at phases I (482.6 K, 466.8 K, 443.3 K) and II (391.2 K, 301.2 K, 78.6 K). The measured spectra in phase II were assigned to the normal modes of SeO 4 tetrahedra vibration. In phase I, this compound shows high electric conductivity due to the hopping of protons. A new Raman line has been found at 826 cm -1 in this high temperature phase. It is suggested that this line is caused by the stretching mode of a single Se–O bond in SeO 4 tetrahedra, accompanied by destruction and reconstruction of hydrogen bonds.

Optical Disk Readout Analysis Using an Extended Point Spread Function.

We present a method to calculate the readout signals from optical disks and their applications. Our method is based on a convolution operation of marks recorded on a disk and an extended point spread function (EPSF). Our method can be applied to the case where the marks are recorded in a groove and the photodetector has an arbitrary shape. Four analyses examples are reported: analysis of the tracking error detection method termed the differential phase detection (DPD), focus shift dependency of readout signal jitter when the marks are recorded in a groove, EPSF for land and groove readout, and a compatible readout method for digital versatile disks and compact disks.

Negative Isotope Effect on the Superionic Transition Point and the Behavior of the SO4 ν1-Internal Modes in K3H(SO4)2 and K3D(SO4)2

The superionic transitions of protonated K3H(SO4)2 and deuterated K3D(SO4)2 insulators are investigated using Raman scattering and differential scanning calorimetry (DSC) measurements. DSC indicates that the superionic transition temperature of K3D(SO4)2 is approximately 9 K lower than that of K3H(SO4)2. This confirms the negative isotope effect on the superionic transition temperature of this compound and suggests that the bonding strength of D bonds is lower than that of H bonds. Raman scatterings from K3H(SO4)2 and K3D(SO4)2 show that the ν1-normal vibration mode of the SO4 tetrahedra consists of two rather than one band, despite the symmetry of the vibration mode. The oscillation frequency of the ν1-mode for SO4 tetrahedra in K3D(SO4)2 is higher than that for K3H(SO4)2, which is thought to be closely related to the negative isotope effect on the transition temperature.

Phenomenological Dynamical Theory of KH2PO4 in Paraelectric Phase

The Slater and the Takagi models of the ferroelectric phase transition in KH 2 PO 4 (KDP) have been extended to the model that the number of each proton configuration depends on time. We adopt the two proton configurations proposed by Silsbee et al . besides the Slaters and the Takagis configurations. The dynamical susceptibility, χ(ω), is obtained in the form of the sum of two Debye-type functions, where we have gained two relaxation times with different temperature dependence. One of them, τ - tends to infinity when temperature approaches the transition point from the paraelectric region. This feature is very similar to the results of Yoshimitsu et al. Next, we determine the three orientation energies, e 0 , e 1 and e 2 , using some experimental results and then calculate two relaxation times numerically. The polarization relaxation mode is found in the narrow frequency region within 0∼0.5 c m -1 .

Raman Spectroscopic Investigation of the Superionic Phase Transition in Cs3D(SO4)2

The superionic phase transition of Cs3D(SO4)2 (TCDS) is investigated using Raman scattering and differential scanning calorimetry (DSC) measurements. It is confirmed that TCDS undergoes a superionic phase transition at 415.1 K. The result of the Raman scattering measurement at room temperature shows that TCDS does not form the dimer structure SO4⋯D⋯SO4. It suggests that this phase transition is not caused by the destruction of hydrogen bonds forming a dimer structure.