摘要
CH3 internal rotation is one of the typical large amplitude motions in polyatomic molecules,the spectral analysis and theoretical calculations of which,were developed by Li-Hong Xu and Jon Hougen.We observed a Doppler-free high-resolution and high-precision spectrum of 9-methylanthracene(9MA)by using the collimated supersonic jet and optical frequency comb techniques.The potential energy curve of CH3 internal rotation is expressed by a six-fold symmetric sinusoidal function.It was previously shown that the barrier height(V6)of 9MA-d12 was considerably smaller than that of 9MA-h12[M.Baba,et al.,J.Phys.Chem.A 113,2366(2009)].We performed ab initio theoretical calculations of the multicomponent molecular orbital method.The barrier reduction by deuterium substitution was partly attributed to the difference between the wave functions of H and D atomic nuclei.
