Institute for Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt/Main, Germany.
J Chem Phys. 2012 Feb 14;136(6):064107. doi: 10.1063/1.3682324.
An earlier proposed approach to molecular response functions based on the intermediate state representation (ISR) of polarization propagator and algebraic-diagrammatic construction (ADC) approximations is for the first time employed for calculations of nonlinear response properties. The two-photon absorption (TPA) spectra are considered. The hierarchy of the first- and second-order ADC∕ISR computational schemes, ADC(1), ADC(2), ADC(2)-x, and ADC(3/2), is tested in applications to H(2)O, HF, and C(2)H(4) (ethylene). The calculated TPA spectra are compared with the results of coupled cluster (CC) models and time-dependent density-functional theory (TDDFT) calculations, using the results of the CC3 model as benchmarks. As a more realistic example, the TPA spectrum of C(8)H(10) (octatetraene) is calculated using the ADC(2)-x and ADC(2) methods. The results are compared with the results of TDDFT method and earlier calculations, as well as to the available experimental data. A prominent feature of octatetraene and other polyene molecules is the existence of low-lying excited states with increased double excitation character. We demonstrate that the two-photon absorption involving such states can be adequately studied using the ADC(2)-x scheme, explicitly accounting for interaction of doubly excited configurations. Observed peaks in the experimental TPA spectrum of octatetraene are assigned based on our calculations.
一种基于极化算符的中间态表示（ISR）和代数图论（ADC）近似的分子响应函数的早期方法，首次被用于计算非线性响应性质。本文考虑了双光子吸收（TPA）光谱。采用第一性原理和二阶 ADC∕ISR 计算方案（ADC(1)、ADC(2)、ADC(2)-x 和 ADC(3/2)）的层次结构，对 H(2)O、HF 和 C(2)H(4)（乙烯）进行了测试。将计算的 TPA 光谱与耦合簇（CC）模型和含时密度泛函理论（TDDFT）计算的结果进行了比较，以 CC3 模型的结果作为基准。作为一个更现实的例子，使用 ADC(2)-x 和 ADC(2)方法计算了 C(8)H(10)（辛四烯）的 TPA 光谱。将结果与 TDDFT 方法和早期计算结果以及可用的实验数据进行了比较。辛四烯和其他多烯分子的一个显著特征是存在具有增加的双激发特征的低能激发态。我们证明，使用 ADC(2)-x 方案可以充分研究涉及这些状态的双光子吸收，该方案明确考虑了双激发组态的相互作用。基于我们的计算，对辛四烯实验 TPA 光谱中的观察到的峰进行了归属。
