Ohrn Anders, Karlström Gunnar
Department of Theoretical Chemistry, Chemical Center, P.O.B. 124, S-221 00 Lund, Sweden.
J Phys Chem A. 2006 Feb 9;110(5):1934-42. doi: 10.1021/jp055678l.
The solvent shift to the fluorescence transition pi --> n in formaldehyde in aqueous solution is theoretically analyzed. The solvent model has explicit representation of the solvent and uses the complete active space state interaction (CASSI) method to obtain a description of the wave function of the solute similar to what the complete active space self-consistent-field (CASSCF) method would give. In the description of the solute-solvent interaction the discrete set of solvent molecules perturb the solute not only through an electrostatic perturbation but also through a nonelectrostatic operator. The latter describes in a way analogous to pseudopotential theory the effect the Pauli principle has on the solute embedded in the solvent. This way the exchange repulsion between solute and solvent is accounted for which therefore can be anisotropic. The best estimate of the average shift is a blue shift of 0.003 eV, and for the current transition the nonelectrostatic perturbation broadens the distribution but has no significant effect on the average shift.
对水溶液中甲醛荧光跃迁π→n的溶剂位移进行了理论分析。溶剂模型明确表示了溶剂，并使用完全活性空间态相互作用（CASSI）方法来获得与完全活性空间自洽场（CASSCF）方法类似的溶质波函数描述。在溶质 - 溶剂相互作用的描述中，离散的溶剂分子集不仅通过静电微扰而且通过非静电算符来扰动溶质。后者以类似于赝势理论的方式描述了泡利原理对嵌入溶剂中的溶质的影响。通过这种方式，考虑了溶质与溶剂之间的交换排斥，因此这种排斥可以是各向异性的。平均位移的最佳估计是蓝移0.003 eV，对于当前跃迁，非静电微扰拓宽了分布，但对平均位移没有显著影响。
