Resonance structure in electron–N2 scattering around 11.5 eV: high-resolution measurements, ab initio calculations and line shape analyses
Resonance structure in electron–N2 scattering around 11.5 eV: high-resolution measurements, ab initio calculations and line shape analyses
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11.5 eV 附近电子-N2 散射的共振结构：高分辨率测量、从头计算和线形分析
DOI：
10.1088/0953-4075/42/21/215202
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
W. Meyer
中科院分区：
文献类型：
--
作者：
T. Hoffmann;M. Allan;K. Franz;M. Ruf;H. Hotop;G. Sauter;W. Meyer
使用能量宽度约为 6 和 13 meV 的两种不同的实验装置，我们获得了在窄 N−2(R2Σ+g) 共振周围能量范围内 N2 分子电子散射的角度微分 (10°–180°) 弹性和振动非弹性截面的能量依赖性的显着改善结果。该共振的能量位置和自然宽度分别确定为 11.497(2) eV 和 1.3(2) meV。从头计算势能曲线是通过 CCSD(T) 计算中性 N2(X1Σ+g) 和 N*2(E3Σ+g) 态以及 N−2(R2Σ+g) 共振态获得的。它们相当准确地证实了测量到的共振能量，并为相关振动状态提供了准确的能量间距和重叠积分。通过应用共振和非共振散射过程的干扰模型，对选定散射角的共振线形状进行详细分析。它提供了共振宽度与绝对 DCS 之间的联系，并在共同基础上描述了弹性和振动激励过程。通过它们的大小和符号，振动重叠积分可以确定观察到的法诺型线形状，并解释相邻振动共振峰的相反不对称性和强度变化。通过对非共振振幅进行适当的参数化，可以对观察到的形状进行微调。还提出了从阈值（接近 11.88 eV）到 13.4 eV 形成亚稳态 N*2(E3Σ+g) 能级的高分辨率激发函数。
Using two different experimental setups with energy widths of about 6 and 13 meV, we obtained significantly improved results for the energy dependence of angle-differential (10°–180°) elastic and vibrationally inelastic cross sections for electron scattering from N2 molecules in the energy range around the narrow N−2(R2Σ+g) resonance. The energy location and the natural width of this resonance are determined as 11.497(2) eV and 1.3(2) meV, respectively. Ab initio potential energy curves are obtained from CCSD(T) calculations for the neutral N2(X1Σ+g) and N*2(E3Σ+g) states as well as for the N−2(R2Σ+g) resonance state. They corroborate quite accurately the measured resonance energy and provide accurate energy spacings and overlap integrals for the pertinent vibrational states. A detailed analysis of resonance line shapes for selected scattering angles is performed by applying a model for the interference of resonant and nonresonant scattering processes. It provides a link between the resonance width to absolute DCS and describes elastic and vibrational excitation processes on a common basis. Through both their size and sign, vibrational overlap integrals are shown to determine the observed Fano-type line shapes and account for the opposite asymmetries and intensity changes of adjacent vibrational resonance peaks. Fine-tuning of the fits to the observed shapes is achieved by proper parametrization of the nonresonant amplitudes. A highly resolved excitation function for the formation of the metastable N*2(E3Σ+g) level from threshold (near 11.88 eV) to 13.4 eV is also presented.