Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
Data Center for High Energy Density Physics, Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088, People's Republic of China.
J Chem Phys. 2019 Mar 7;150(9):094302. doi: 10.1063/1.5087603.
The generalized oscillator strengths of the low-lying valence-shell excitations of N, O, and CH have been studied by the high-energy electron scattering, the high-resolution inelastic X-ray scattering, and the multireference single- and double-excitation configuration-interaction methods. Good agreement between the present electron-scattering results and the X-ray-scattering ones for the aΣ v=0 and aΣ v=1+bΠv=0 excitations of N and the AΔ excitation of O is achieved in the small squared momentum transfer region, while obvious discrepancies among them are observed in the large squared momentum transfer region. This phenomenon indicates that the first Born approximation is satisfied in the small squared momentum transfer region, while it does not hold in the large squared momentum transfer region at an incident electron energy of 1500 eV, in view of the fact that the first Born approximation is satisfied in the X-ray scattering. In addition, the present calculation for the aΣ excitation shows that the traditional assigned v' = 0 and 1 of the aΣ excitation correspond to v' = 9 and 13 of the 2Σ excitation and reproduces the X-ray-scattering results of the aΣ v=0 excitation very well except the ones in the small squared momentum transfer region. We also report the generalized oscillator strengths of the à + B̃ excitations of CH, and its profile shows that the bending geometry has great influence on the transition feature.
已通过高能电子散射、高分辨率非弹性 X 射线散射和多参考单激发和双激发组态相互作用方法研究了 N、O 和 CH 的低价壳层激发的广义振子强度。在小平方动量转移区域，本电子散射结果与 N 的 aΣ v=0 和 aΣ v=1+bΠ v=0 激发以及 O 的 AΔ 激发的 X 射线散射结果吻合良好，而在大平方动量转移区域，它们之间存在明显差异。考虑到 X 射线散射中满足第一 Born 近似，这种现象表明在小平方动量转移区域满足第一 Born 近似，而在 1500eV 入射电子能量下的大平方动量转移区域不满足第一 Born 近似。此外，对于 aΣ 激发的本计算表明，aΣ 激发的传统分配 v'=0 和 1 对应于 2Σ 激发的 v'=9 和 13，并且除了在小平方动量转移区域之外，很好地再现了 aΣ v=0 激发的 X 射线散射结果。我们还报告了 CH 的 Ã + B̃ 激发的广义振子强度，其轮廓表明弯曲几何形状对跃迁特征有很大影响。
