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Investigation of optical spectra of small numbers of molecules in condensed matter

凝聚态物质中少量分子的光谱研究

基本信息

批准号：
06452046
负责人：
KUSHIDA Takashi
金额：
$ 4.8万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

Recently, we have obtained a number of significant results on optical spectra of molecules in polymers, glasses and proteins by means of site-selective spectroscopies. However, information obtained by these techniques is limited to ensemble averages over many molecules having the same optical transition energy. In order to obtain more detailed information, we measured fluoreascence excitation spectra of small numbers of terrylene molecules in hexadecane in the 2-5K temperature range. An Ar^+-laser-prmped single-mode dye laser was employed for the excitation. The peak frequency of the single-molecule spectrum was found to depend on the applied pressure linearly. From this result, the compressibility of hexadecane was determined to be 0.052GPa^<-1>. The temperature dependence of the spectral width was dependent on each molecule, and the observed nonlinear dependence was explained by the coupling of two-level systems to the guest molecule. On the other hand, it is theoretically predicted that the contribution fo small numbers of molecular groups manifests itself in the spectral shape of a persistent hole burned in the absorption spectrum of dyedoped condensed matter. We performed a temperature cycling hole-burning experiment in H_2-substituted myoglobin, and found that there exists only one molecular group in a protein molecule that corresponds to the two-level systems making flips in the 4-70K temperature range. We further determined the coupling strength between the heme electron and the two-level systems in myoglobin.

近年来，我们利用择位光谱学对聚合物、玻璃和蛋白质中分子的光谱进行了研究，取得了一些有意义的结果。然而，通过这些技术获得的信息仅限于具有相同光学跃迁能量的许多分子的系综平均值。为了获得更详细的信息，我们在2- 5 K温度范围内测量了少量三萘嵌苯分子在十六烷中的荧光激发光谱。采用Ar^+激光脉冲驱动的单模染料激光器进行激发。发现单分子光谱的峰值频率与外加压力成线性关系。根据该结果，确定十六烷的压缩率为0.052GPa^<-1>。光谱宽度的温度依赖性依赖于每个分子，所观察到的非线性依赖性解释了二能级系统的客体分子的耦合。另一方面，理论上预测，少量分子团的贡献表现为染料掺杂凝聚态吸收光谱中的持续烧孔的光谱形状。我们对H_2取代的肌红蛋白进行了温度循环烧孔实验，发现在4- 70 K温度范围内，蛋白质分子中只存在一个对应于二能级系统翻转的分子团。我们进一步确定了血红素电子与肌红蛋白中二能级系统的耦合强度。