Study of hyper-Raman scattering excited by dye-laser for spectroscopic use in solids

1.首次用重复脉冲染料激光器成功地观测到固体中光学声子的超喇曼信号。为此，我们研制了一套高灵敏度的检测系统。因此，我们首次在实验上研究了TiO_2和SrTiO_3晶体中超喇曼散射效率的频散，在一定范围内，入射光的两倍2HWI和散射光的两倍HWS跨越基本吸收边缘。结果表明，当2hwi从下面接近带隙Eg时，90 °散射几何中允许声子模的效率显著增加。这一事实将使人们能够在未来进行更灵敏的超拉曼实验。3.我们还表明，上述结果可以合理地解释为双光子持续共振与图4。我们发现金红石晶体中后向散射几何中通常被禁戒的纵向声子在带隙处表现出尖锐而显著的双光子共振行为。其起源可能是由于q依赖的Fro^^“巫妖相互作用引起的与激子的共振。在SrTiO_3中也观察到了类似的由LO声子引起的共振行为。我们将这种现象解释为弗罗巫妖相互作用的结果。因此，在上述意义上的共振超拉曼光谱是一种很有前途的技术，以解开特定的临界点的电子能带结构的固体，特别是在紫外区。注意，光跃迁能量的一半的光子能量是足够的。

1. For the first time, we have succeeded in observing the hyper-Raman signals of optic phonon in solids by using a repetitively pulsed dye laser. For this purpose, we have developed a high-sensitive detection-system.2. Thereby, we have for the first time studied experimentally the frequency dispersion of the hyper-Raman scattering efficiency in Tio_2 and SrTiO_3 crystals, in such a range that the relevant photon energies, i.e., twice the incident one, 2hwi and the scattered one, hws are across the fundamental absorption edge. As the result, it is found that the efficiency of the allowed phonon modes in the 90ﾟ scattering geometry increases remarkably, as 2hwi approaches the band gap Eg from below. This fact will enable one to perform more sensitive hyper-Raman experiments in the future.3.We have also shown that the above result can be reasonably interpreted in terms of a two-photon ongoing resonance with Eg.4. We have found that the forbidden longitudinal phonon normally forbidden in the backward scattering geometry in a rutile crystal shows a sharp and striking two-photon resonant behavior at the band gap. The origin may be attributed to the resonance with the excitons due to the q-dependent- Fro^^"lich interaction. we have also observed a similar resonant behavior due to the LO phonon in SrTiO_3. we have interpreted this phenomenon as arising from the Fro^^"lich interaction.5. As a consequence, the resonant hyper-Raman spectroscopy in the above sense is a promising technique to unravel specific critical points of electronic band structure in solids, particularly in the ultraviolet region. It is noted that a photon energy of half the optical transition energy is sufficient.