The time-independent eigenstate-free Raman wavefunction approach for calculating anharmonic vibronic spectra has been extended for the calculation of Herzberg–Teller contributions on the basis of an n-mode expansion of the transition electric dipole moment surface. This allows for the efficient simulation of Franck–Condon dark vibronic spectra. In addition, vibrational angular momentum terms have been implemented into this formalism, as they are important for an accurate description of vibrational wavefunctions spanning double-well potentials. This approach has been used to compute the FC-forbidden vibronic spectrum of the n → π^* transition of formaldehyde based on a potential energy and transition dipole moment surfaces obtained from explicitly correlated multi-reference configuration interaction calculations. An extensive analysis of the resulting vibronic structure is provided, which allows for a detailed assignment and interpretation of the experimental spectrum.

中文翻译：

---

时间无关的拉曼波函数理论中非康顿效应的解释：甲醛的S1←S0振动吸收光谱的计算

在过渡电子偶极矩表面的n模展开的基础上，扩展了用于计算非谐振动频谱的非时间无关本征态拉曼波函数方法，用于计算Herzberg-Teller贡献。这可以有效地模拟弗兰克-康登黑暗振动光谱。另外，振动角动量项已被应用到这种形式主义中，因为它们对于精确描述跨越双阱势的振动波函数很重要。该方法已用于计算n → π ^*的FC禁止的振动光谱根据势能和过渡偶极矩表面得出的甲醛过渡态，该表面由明确相关的多参考构型相互作用计算获得。提供了对所得振动子结构的广泛分析，从而可以详细分配和解释实验光谱。