Center for Oxygen Microscopy and Imaging and Lundbeck Foundation Center for Theoretical Chemistry, Department of Chemistry, University of Arhus, DK-8000 Arhus C, Denmark.
J Chem Phys. 2009 Oct 21;131(15):154101. doi: 10.1063/1.3246349.
Quadratic response functions are derived and implemented for a vibrational configuration interaction state. Combined electronic and vibrational quadratic response functions are derived using Born-Oppenheimer vibronic product wave functions. Computational tractable expressions are derived for determining the total quadratic response contribution as a sum of contributions involving both electronic and vibrational linear and quadratic response functions. In the general frequency-dependent case this includes a new and more troublesome type of electronic linear response function. Pilot calculations for the FH, H(2)O, CH(2)O, and pyrrole molecules demonstrate the importance of vibrational contributions for accurate comparison to experiment and that the vibrational contributions in some cases can be very large. The calculation of transition properties between vibrational states is combined with sum-over-states expressions for analysis purposes. On the basis of this some simple analysis methods are suggested. Also, a preliminary study of the effect of finite lifetimes on quadratic response functions is presented.
二次响应函数是为一个振动组态相互作用态推导和实现的。使用 Born-Oppenheimer 振子产物波函数推导出了组合电子和振动二次响应函数。导出了计算总二次响应贡献的可计算表达式，该贡献是电子和振动线性和二次响应函数的贡献之和。在一般的频率相关情况下，这包括一种新的、更麻烦的电子线性响应函数。针对 FH、H(2)O、CH(2)O 和吡咯分子的初步计算表明，振动贡献对于与实验的准确比较非常重要，并且在某些情况下振动贡献可能非常大。振动态之间的跃迁性质的计算与求和态表达式结合起来进行分析。在此基础上，提出了一些简单的分析方法。此外，还初步研究了有限寿命对二次响应函数的影响。
