Soft mode in cubic PbTiO3by hyper-Raman scattering

Silent soft mode in hexagonal barium titanate observed by hyper-Raman scattering.

In a recent paper' Inoue et al. discussed a soft optical phonon that drives the second-order phase transition from hexagonal BaTi03, space group P63/mme (D6t, ), to a lower-symmetry structure at T, =222 K. The new phase is not ferroelectric and its structure is not known. The soft mode is Raman and infrared inactive and therefore is a so-called "silent" mode. Using hyper-Raman scattering, Inoue...

Resonant Raman scattering in cubic and hexagonal boron nitride

We measured firstand second-order Raman scattering in cubic and hexagonal boron nitride using excitation energies in the visible and in the UV. The nonresonant first-order Raman susceptibilities for cubic and hexagonal BN are 1 and 10 Å2, respectively. Raman scattering is thus very powerful in detecting the hexagonal phase in mixed thin boron nitride films. In cubic BN the constant Raman sucsep...

SOFT-MODE PHONONS in SrTiO3 THIN FILMS STUDIED by FAR-INFRARED ELLIPSOMETRY and RAMAN SCATTERING

We report the experimental studies of the vibrational spectra of SrTiO3 films with the thickness of 1 μm grown by pulsed laser deposition. Fourier-transform infrared ellipsometry between 30 and 700 cm and electric field-induced Raman scattering techniques have been utilized for investigation of the phonon behavior. These results can be used for comparison with the low-frequency measurements of ...

Nonresonant hyper-Raman and hyper-Rayleigh scattering in benzene and pyridine

Nonresonant hyper-Raman and hyper-Rayleigh spectra excited at 1064 nm are reported for neat benzene and pyridine. The theory of Herzberg-Teller vibronic coupling in nonresonant and preresonant hyper-Raman scattering is developed. Nonresonant hyper-Raman scattering is shown to be vibronically induced by modes that efficiently couple strongly allowed onephoton and two-photon transitions. A weak a...

Stimulated Raman scattering in soft glass fluoride fibers