On the classical microwave and infrared pressure broadening theory for ammonia

摘要

A stochastic Liouville equation has been developed to represent collision effects on the ammonia internal degrees of freedom of inversion, spatial orientation, and the ngr;1fundamental mode of vibration. A modified form of Benhyphen;Reuven's spectral shape function for the microwave spectrum in the ``singlehyphen;line'' approximation is derived and shown to give a good fit to the experimental results for ND3, comparable to the earlier ``manyhyphen;line'' fit, with a distribution of relaxation rates, of Maryott and Kryder. Further, it is shown that the collision induced memory loss in the absorbing dipole moment autocorrelation function determines the pressurehyphen;dependent behavior of the spectral shape function. Examples are given with special consideration of the effects of collision induced dipole reorientations and vibrational phase changes and transitions for the infrared spectrum.