Photocalorimetric Spectroscopy of Excitons in Semiconductor-Energy Dissipation Processes of Photo-excited States-

为了阐明激子-声子散射引起的激子非辐射弛豫过程，在最适合研究激子的半导体晶体β-ZnP_2中，同时测量了激子发光的光热谱和激发谱。主要研究结果如下：1.对于单重态激子，在从1 s纵向激子能量E_L到带隙能量E_g.2的能量范围内，由晶体吸收的光的功率几乎以相等的速率转换为晶体的热加热的功率，其量接近80%。在1 s反射带，单重态激子发光和发热量均减少，这表明在该能区存在共振瑞利散射等其他光学过程.在激子共振n=1至4处，PC信号与发光强度的比率增强。这一事实表明，激子的非辐射衰减率相对于发光的发射率在激子共振处较大.在激发到E//B的三重态激子共振区的情况下，除了未知的背景之外，PC光谱与三重态激子的吸收光谱相当相似。这一事实表明，如果忽略背景，产生三重态激子的吸收光几乎以恒定的速率转化为发热。上述结果在去年夏天举行的凝聚态物质发光和光谱学国际会议上以及日本物理学会的会议上发表。

In order to clarify nonradiative relaxation processes of excitons due to exciton-phonon scattering, simultaneous measurements of photocalorimetric (PC) spectra and excitation spectra of exciton luminescence have been performed in a semiconductor crystal β-ZnP_2, which is one of the most suitable materials for the exciton study. The main results obtained are as follows :1. For singlet excitons, power of the light absorbed by the crystal is converted to that of the thermal heating of the crystal almost at an equal rate, which amounts to nearly 80%, in the energy range from the 1s longitudinal exciton energy E_L to the band gap energy E_g.2. The amounts of both singlet exciton luminescence and heat generation decrease in the 1s reflection band, which suggests the presence of other optical process such as resonant Rayleigh scattering in this energy region.3. The ratio of the PC signal to the luminescence intensity is enhanced at the exciton resonances n=1 to 4. This fact indicates that the rate of the nonradiative decay of excitons relative to the emission of the luminescence is large at the exciton resonances.4. The PC spectrum under excitation into the triplet exciton resonance region with E//b resembles fairly well the absorption spectrum of the triplet exciton besides unknown background. This fact indicates that, if the background is neglected, the absorbed light to create the triplet excitons is converted to the heat generation almost at a constant rate.The results mentioned above were presented at the International Conference on Luminescence and Optical Spectroscopy of Condensed Matter held in the last summer and also at meetings of the Physical Society of Japan.