KS eigenvalue and virtual orbital character of the low-lying orbitals in pyridazine, obtained from a minimal basis set calculation

<b>Table 6.</b> KS eigenvalue and virtual orbital character of the low-lying orbitals in pyridazine, obtained from a minimal basis set calculation. <strong>Abstract</strong> The valence shell electronic states of pyridazine have been studied experimentally, by recording the photoabsorption spectrum, and theoretically, by calculating oscillator strengths and excitation energies. The absolute photoabsorption cross section has been measured between 4 and 40 eV, using synchrotron radiation, and is dominated by prominent bands associated with intravalence transitions. In contrast, structure due to Rydberg excitations is weak. One Rydberg state, belonging to a series converging onto the {\rm \tilde X}\;{}^2{\rm B}_{\rm 2} state limit has been observed and assigned. The accompanying vibrational structure has been characterized by analogy with that in the corresponding photoelectron band. Vibrational progressions associated with Rydberg states belonging to one or more series converging onto the {\rm \tilde A}\;{}^2{\rm A}_{\rm 2} state limit have also been observed. The absorption structure associated with these series is complex and only tentative assignments have been proposed for the Rydberg states. The time-dependent version of density functional theory has been used to calculate oscillator strengths and excitation energies for the optically allowed singlet–singlet valence transitions and also to obtain the excitation energies for electric-dipole-forbidden and/or spin-forbidden transitions. The valence shell photoionization dynamics have been investigated theoretically by calculating photoelectron angular distributions and photoionization partial cross sections of the four outermost orbitals. In addition, the ground state outer valence electronic configuration has been obtained at the complete active space self-consistent field and the N-electron valence state perturbation theory to second-order levels of theory.

**表6.** 极小基组计算所得哒嗪低能轨道的科恩-沈吕九（Kohn-Sham, KS）本征值与虚轨道特征。

**摘要** 本研究通过记录光吸收谱开展实验探究，并通过计算振子强度与激发能开展理论分析，对哒嗪的价层电子态进行了系统研究。本工作利用同步辐射测量了4~40 eV能段内的绝对光吸收截面，该截面以与价内跃迁相关的显著吸收带为主。与之形成鲜明对比的是，里德堡激发所产生的光谱结构相对微弱。研究人员观测到了一个隶属于收敛于${
m ilde X};{}^2{
m B}_{
m 2}$态极限的里德堡态系列的里德堡态，并对其进行了指认。伴随的振动结构通过与对应光电子能带的振动结构类比完成了表征。此外，本研究还观测到了隶属于一个或多个收敛于${
m ilde A};{}^2{
m A}_{
m 2}$态极限的里德堡态系列的里德堡态所对应的振动递进序列。与这些里德堡态系列相关的吸收结构较为复杂，目前仅对该类里德堡态提出了尝试性指认。

本研究采用含时密度泛函理论（time-dependent density functional theory），计算了光学允许的单重态-单重态价态跃迁的振子强度与激发能，同时也获得了电偶极禁阻和/或自旋禁阻跃迁的激发能。此外，本研究通过计算四个最外层轨道的光电子角分布与光致电离分截面，从理论上探究了价层光致电离动力学。同时，本工作在完全活性空间自洽场（complete active space self-consistent field）以及二阶N电子价态微扰理论的理论水平下，得到了基态外层价电子组态。