Study of Microscopic Molecular Environment Through which the Natural Radiative Lifetime is Determined

为了了解有机分子辐射寿命的微观分子环境的性质，在各种专门设计的系统中测量了许多蒽衍生物的荧光寿命。主要研究结果如下：1.测定了几种蒽衍生物在超音速自由射流（气相）和溶液中的辐射寿命。两相中的值可以通过所用溶剂的折射率联系起来，公式为n^2 zeta_f（溶液）=zeta_f（气相）2。通过比较两个阶段的辐射寿命建立的关系在溶液中进一步检查。溶剂的折射率通过施加流体静压而变化。对于荧光量子产率几乎等于1的五种蒽衍生物，除9，10-二甲氧基蒽外，在0.1 ~ 400 MPa的压力范围内均能很好地遵循n^2-关系.围绕中心分子产生的微观分子环境取决于中心分子的形状。这可能导致与n^2-依赖不同的n-依赖。为了证实这一点，POPOP，QUI，BBQ和Bis-MSB，所有这些都是长链形状的荧光寿命上的压力的影响。此外，在稀有气体基质或液滴中进行荧光寿命测量，以获得扩展本研究所需的基础数据。

In order to understand the nature of microscopic molecular environments through which radiative lifetime of organic molecules are determined, the fluorescence lifetimes of a number of anthracene derivatives were measured in a wide variety of specially designed systems. The obtained results are summarized as follows.1. The radiative lifetime is determined for several anthracene derivatives both in supersonic free jets (gas phase) and in solution. The values in the two phases can be related through the refractive index of the solvents used as n^2zeta_f (solution) =zeta_f (gas phase)2. The relation established through a comparison of the radiative lifetimes in the two phases was further examined in solution. The refractive index of the solvent was varied by the application of hydrostatic pressure. For five anthracene derivatives, whose fluorescence quantum yields are practically equal to unity, n^2-relationship was found to be followed excellently over the range of pressure from 0.1 MPa to 400 MPa except for 9, 10-dimethoxyanthracene.3. Microscopic molecular environment created around a central molecule is dependent on the shape of the molecule in the center. This may lead to a n-dependence different from n^2-dependence. To confirm this, the effect of pressure on the fluorescence lifetimes of POPOP, QUI, BBQ and Bis-MSB, all of which are of a long-chain shape. In addition, the fluorescence-lifetime measurements were performed in the rare-gas matrixes or in droplets in order to obtain basic data which are necessary to expand the present study.