Excitation of the symmetric and antisymmetric stretch vibrations of H2O by electron impact
Excitation of the symmetric and antisymmetric stretch vibrations of H2O by electron impact
复制标题
电子碰撞激发 H2O 的对称和反对称伸缩振动
DOI：
10.1088/0953-4075/35/1/106
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
O. Moreira
中科院分区：
文献类型：
--
作者：
M. Allan;O. Moreira
在135°角下，在0.05，0.6和3.0 eV的恒定散射电子能量下，记录到的电子能量损失谱，分辨率为10 meV，表明反对称伸缩振动（001）的激发远小于对称伸缩振动（100）。光谱相减表明，在1 eV处，（001）能级的激发比（100）能级小约5倍。在阈值以上0.6 eV处记录的能带分布表明，ΔJ = 0分支主导（010）和（100）振动的激发，但不存在（001）振动。这表明共振激发对（010）和（100）态是决定性的，而直接偶极机制对（001）态是决定性的。R-矩阵绝热核理论在闭合近似下很好地再现了（010）态的截面，但大大低估了对称伸缩振动的截面，而高估了非对称伸缩振动的截面.
Electron energy loss spectra recorded at 135° at constant scattered electron energies of 0.05, 0.6 and 3.0 eV, and with 10 meV resolution, reveal that the antisymmetric stretch vibration (001) is excited much less than the symmetric stretch vibration (100). Spectra subtraction indicates that the (001) level is excited about 5× less than (100) at 1 eV. Band profiles recorded 0.6 eV above threshold show that the ΔJ = 0 branch dominates the excitation of (010) and (100) vibrations but is absent for the (001) vibration. This indicates that resonant excitation is decisive for the (010) and (100) states but direct dipole mechanism for (001). The R-matrix adiabatic nuclei theory with closure approximation reproduces well the cross section for the (010) state, but dramatically underestimates the cross section for the symmetric stretch vibration and overestimates the cross section for the asymmetric stretch vibration.