This paper investigates in detail the vacuum UV photoabsorption spectrum of trans-1,2-C₂H₂Cl₂ in the 5–20 eV range using synchrotron radiation. Quantum chemical calculations are applied to the electronic transitions. Particular attention has been paid to the 2a_u(π)→2b_g(π*) transition included in the broad band observed at 6.30 eV. The Rydberg 2a_u(π)→R3s transition is presumably observed at 6.27 eV. Below 6.0 eV the structure(s) are assigned to π→σ* transition(s). The abundantly structured spectrum observed between 7.0 eV and 12.0 eV has been analyzed in terms of vibronic transitions to ns- ($\overline{\delta }$=0.844) and nd/4f- ($\overline{\delta }$=0.03/0.011) Rydberg states, converging to the 2a_u⁻¹ ionization continuum, to two series of np- ($\overline{\delta }$= 0.66 and 0.40) states converging to the 5a_g⁻¹ continuum, to ns- ($\overline{\delta }$=0.983) and nd- ($\overline{\delta }$= –0.06) states converging to the 4b_u⁻¹ continuum and to two np-type ($\overline{\delta }$= 0.51 and 0.26) series converging to the 1b_g⁻¹ continuum. These data are complemented by an analysis of the vibrational structure of the individual Rydberg states. Comparisons with previously reported values are provided. Several other spectral features Table S2 (see Supplementary Material) in the 12–20 eV range are tentatively assigned to transitions to Rydberg states converging to higher ionic excited states of trans-1,2-C₂H₂Cl₂. Assignments of the vibrational structure of some of these transitions are also proposed.

本文详细研究了使用同步加速器辐射在5-20 eV范围内反式1,2-C ₂ H ₂ Cl ₂的真空紫外光吸收光谱。量子化学计算应用于电子跃迁。特别注意的是在6.30 eV观察到的宽带中包含的2a _u（π）→2b _g（π*）跃迁。Rydberg 2a _u（π）→R3s跃迁大概在6.27 eV处观察到。低于6.0 eV，结构被指定为π→σ*跃迁。已经分析了从7.0 eV到12.0 eV之间的结构丰富的光谱，从向ns-（$\overline{\delta }$= 0.844）和nd / 4f-（$\overline{\delta }$= 0.03 / 0.011）Rydberg态（收敛到2a _u ^-1电离连续体）到两个np-（$\overline{\delta }$= 0.66和0.40）状态收敛到5a _g ^-1连续体，到ns-（$\overline{\delta }$= 0.983）和nd-（$\overline{\delta }$= –0.06）状态收敛到4b _u ^-1连续体和两个np型（$\overline{\delta }$= 0.51和0.26）级数收敛到1b _g ^-1连续体。这些数据通过对单个里德堡状态的振动结构的分析得到补充。提供与以前报告的值的比较。暂定将12–20 eV范围内的其他几个光谱特征表S2（请参阅补充材料）分配给转变为Rydberg态的跃迁，并收敛到反式1,2-C ₂ H ₂ Cl _2的更高离子激发态。还提出了其中一些过渡的振动结构分配。