Mekhtiev MA, Godfrey PD, Hougen JT
Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland, 20899
J Mol Spectrosc. 1999 Apr;194(2):171-178. doi: 10.1006/jmsp.1998.7782.
Linestrengths have been obtained for methanol based on matrix elements of the dipole moment operator evaluated in a set of torsion-rotation eigenfunctions. The latter were obtained from the parameters and effective Hamiltonian giving the best spectral fit available for a data set containing J </= 20, K </= 14, and upsilont </= 1 microwave and far infrared transitions. The dipole moment function was represented as a Fourier expansion in the torsional angle gamma. Values for the permanent components µa and µb were obtained from experiment; values for their cos 3gamma variation and for the sin 3gamma variation of µc were obtained from quantum chemistry molecular orbital calculations. The approach described allows calculation of the linestrength for any transition which satisfies the general selection rule A1 left and right arrow A2 or E left and right arrow E. A complete set of such linestrengths for all methanol torsion-rotation transitions involving levels with J </= 22, K </= 14, and upsilont </= 2, and with intensities and frequencies above the rather small cutoff limits of 10(-6) D2 and 1 kHz, respectively, together with individual contributions from the permanent and gamma-varying dipole moment components, have been tabulated and are available on request (ftp.monash.edu.au/pub/chem/1998a). Copyright 1999 Academic Press.
基于在一组扭转-转动本征函数中评估的偶极矩算符的矩阵元，已获得甲醇的谱线强度。后者是从参数和有效哈密顿量得到的，这些参数和有效哈密顿量能对包含(J\leq20)、(K\leq14)以及(\upsilon_t\leq1)的微波和远红外跃迁的数据集给出最佳的光谱拟合。偶极矩函数表示为扭转角(\gamma)的傅里叶展开。永久分量(\mu_a)和(\mu_b)的值通过实验获得；它们的(\cos3\gamma)变化以及(\mu_c)的(\sin3\gamma)变化的值通过量子化学分子轨道计算获得。所描述的方法允许计算满足一般选择规则(A_1\leftrightarrow A_2)或(E\leftrightarrow E)的任何跃迁的谱线强度。对于所有涉及(J\leq22)、(K\leq14)以及(\upsilon_t\leq2)的能级且强度和频率分别高于相当小的截止极限(10^{-6}D^2)和(1kHz)的甲醇扭转-转动跃迁，完整的此类谱线强度集，连同永久和随(\gamma)变化的偶极矩分量的单独贡献，已制成表格并可应要求获取（ftp.monash.edu.au/pub/chem/1998a）。版权所有1999年学术出版社。
