Quasielastic light scattering in rutile,ZnSe, silicon, andSrTiO3

Abstract

Quasielastic light scattering ͑QELS͒ has been investigated in the crystals of TiO 2 ͑rutile͒, ZnSe, silicon, and SrTiO 3 . The temperature dependence of the linewidth for the QELS has been measured in detail by backward light scattering interferometry and by impulsive stimulated thermal scattering technique in the temperature range from 5 to 670 K. The quasielastically scattered spectra observed consist of two components, which can be classified into two types, namely, types I and II, depending on the linewidth. The analyses have shown that the linewidth of the QELS I changes from the well-known q 2 to a q 1 dependence with either decreasing temperature or increasing q, where q is the wave-vector transfer in the scattering experiment. It has been found that the linewidth of the QELS I in arbitrary phonon regimes including "hydrodynamic," "collisionless," and "intermediate" can be roughly estimated solely in terms of average sound velocity and the "phonon Knudsen number" ql, where l is the mean free path of thermal phonons. A broad doublet spectrum, which was first reported by Hehlen et al. in Phys. Rev. Lett. 75, 2416 ͑1995͒, has been observed in SrTiO 3 at low temperatures, and its origin has been also discussed in terms of phonon Knudsen number.

High-resolution temperature-dependent Brillouin scattering studies of ferroelectricK3Nb3O6(BMączka1, Hanuza2, Kojima3 2008Phys. Rev. B

“…If CP is due to the second order Raman effect, its bandwidth usually extends to a few cm −1 at room temperature. 16,30 Our former vibrational studies of KNBO showed that bandwidths of the Raman lines very quickly increase with increasing temperature for this material up to even 30 cm −1 at 550 K temperature. 33 Therefore, it can be expected that the second order Raman processes would lead to appearance of a very broad CP at high temperatures.…”

“…14,16,[28][29][30][31] If CP is due to heat conduction process, the FWHM should be proportional to the square of the wave vector transfer. 28,30 The small size of the studied crystals did not allow us to check the dependence of the FWHM on the wave vector.…”

“…14,16,[28][29][30][31] If CP is due to heat conduction process, the FWHM should be proportional to the square of the wave vector transfer. 28,30 The small size of the studied crystals did not allow us to check the dependence of the FWHM on the wave vector. Since, however, former studies showed that FWHM of CP due to heat diffusion is usually much smaller than in our case, 30,32 and its bandwidth should decrease with increasing temperature, 30 the assignment of the CP to this origin is unlikely.…”

“…28,30 The small size of the studied crystals did not allow us to check the dependence of the FWHM on the wave vector. Since, however, former studies showed that FWHM of CP due to heat diffusion is usually much smaller than in our case, 30,32 and its bandwidth should decrease with increasing temperature, 30 the assignment of the CP to this origin is unlikely. If CP is due to the second order Raman effect, its bandwidth usually extends to a few cm −1 at room temperature.…”

Измерение Времени Жизни Колебательных Состояний Молекул ДНК В Функционализированных Комплексах Полупроводниковых Квантовых Точек

“…Развитые подходы многозонного резонансного рассеяния света [24][25][26][27] . В последующие годы теория многозонного резонансно-го рассеяния света и развитые подходы [24][25][26][27] были подтверждены для многих полупроводниковых матери-алов -от объемных (например, [7]) до низкоразмер-ных наноструктур, включая квантовые точки [8,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. В низкоразмерных наноструктурах формирование боль-шого числа экситонных уровней энергии обусловливает наиболее яркое проявление механизма многозонного резонансного неупругого рассеяния света.…”