High Order Centrifugal Distortion Corrections to Energy Levels of Asymmetric Top Molecules

High order centrifugal distortion terms have been derived and added to the effective Hamiltonian of asymmetric top molecules. Based on this Hamiltonian, a program in Fortran 77 has been developed for spectral analysis of asymmetric top molecules. The high order centrifugal distortion terms are found to be non-negligible even for the low-lying rotational transitions of molecules, such as H₂¹⁸O, subjected to severe centrifugal distortion effect, and for the high-lying rotational transitions of molecules, such as ¹⁴N¹⁶O₂ subjected to the moderate centrifugal distortion effect.