Study of transient absorption and emission spectra of reaction Intermediates using the stretched polymer film method.

利用高分子薄膜拉伸技术结合纳秒激光闪光光解，研究了二苯甲酮及其甲氧基衍生物的偏振瞬态吸收光谱。为了评估我们所构建的系统所获得的数据的可靠性，我们在拉伸聚乙烯醇[PVA]薄膜中测量了蒽的偏振三重态-三重态吸收光谱并进行了分析。结果与混合晶体的测量结果一致，证明了该系统可用于偏振瞬态光谱的测量。在激光照射后20-40ns，测量了二苯甲酮及其甲氧基衍生物在拉伸PVA薄膜中的偏振三重态-三重态吸收光谱。确定了各吸收带的过渡矩方向。分析了甲氧基引入引起的光谱变化。结果表明，在450nm左右出现了短轴极化的吸收带，在650nm以上出现了长轴极化的吸收带。通过测量二苯甲酮在266nm激光照射400ns时的瞬态光谱，测定了拉伸后的PVA薄膜中二苯甲酮酮基自由基的偏振吸收光谱。分析结果与伽玛辐照对聚乙烯醇薄膜中产生的基自由基的测定结果一致。这些成果的一部分在比利时鲁汶举行的第14届IUPAC光化学研讨会上发表。

Polarized transient absorption spectra of benzophenone and its methoxyl derivatives were studied by use of the stretched polymer film technique combined with nano-second laser flash photolysis. To estimate reliability of the data obtained by our system constructed, polarized triplet-triplet absorption spectrum of anthracene were measured in the stretched poly(vinyl alcohol) [PVA] film and analyzed. The results are consistent with those obtained by using the mixed crystal, and it is confirmed that our system is available for measurements of polarized transient spectra. Polarized triplet-triplet absorption spectra of benzophenone and its methoxyl derivatives were measured at 20-40ns after the laser flash in the stretched PVA film. Direction of transition moment of each absorption band was determined. Spectral change induced by introduction of methoxyl group(s) was analyzed. It was made clear that absorption band with short-axis polarization appeared around 450nm, and one with long-axis polarization was observed longer than 650nm. By measuring transient spectra of benzophenone at 400 ns after the 266nm laser flash, polarized absorption spectra of benzophenone ketyl radicals were determined in the stretched PVA film. Analytical results were consistent with those obtained for ketyl radicals produced in PVA film by gamma-irradiation. A part of these results was presented in the 14-th IUPAC symposium on Photochemistry held in Leuven, Belgium.