Relative intensities in the vibrational structure of the Ã(1)A(u)(C(2h))-&Xtilde;(1)Sigma(+)(g)(D(infinityh)) electronic transition of acetylene are calculated. The calculation takes account of the large change of geometry and the change in the normal coordinates (the Dushinskií effect) between the two states. Because conventional vibrational wavefunctions for a nonlinear state do not behave correctly at linear geometries the vibrational integrals are only evaluated approximately. The transition ((1)Sigma(u)(-)-(1)Sigma(+)(g)) is forbidden at linear geometries, and so calculations are performed without and with a factor proportional to the angle of bend from linearity. Good agreement with experiment is obtained for the first few quanta of the absorption spectrum, lending support to the Ã-state harmonic potential of Tobiason et al., J. Chem. Phys. 99, 5762 (1993). Qualitative agreement is obtained for the emission spectrum (Jacobson and Field, J. Phys. Chem. 104, 3073 (2000)) when allowance is made for anharmonicity in the &Xtilde; state, but more quantitative agreement will require improvements in the empirical potential of the &Xtilde;-state, or an ab initio potential to higher energies than available at present. Copyright 2001 Academic Press.

中文翻译：

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乙炔的 ÖX̃ 电子跃迁中计算的振动强度

计算了乙炔的 ?(1)A(u)(C(2h))-&Xtilde;(1)Sigma(+)(g)(D(infinityh)) 电子跃迁的振动结构中的相对强度。计算考虑了几何的巨大变化和两种状态之间法线坐标的变化（杜辛斯基效应）。由于非线性状态的常规振动波函数在线性几何形状下表现不正确，因此只能近似地评估振动积分。过渡 ((1)Sigma(u)(-)-(1)Sigma(+)(g)) 在线性几何中是被禁止的，因此计算时不使用和使用与线性弯曲角度成正比的因子。吸收光谱的前几个量子与实验非常吻合，支持 Tobiason 等人，J. Chem。物理。99, 5762 (1993)。当考虑到 &Xtilde; 中的非谐性时，就获得了发射光谱的定性一致性 (Jacobson and Field, J. Phys. Chem. 104, 3073 (2000))。状态，但更多的定量一致性将需要改进 &Xtilde; 状态的经验潜力，或者比目前可用的更高能量的从头开始的潜力。版权所有 2001 学术出版社。