Efficient calculation of molecular constants and transition intensities in weakly bound species from JÄ0 eigenstates: Benzene-Ar as test case

In application to benzene-Ar we test a procedure that makes use of conveniently calculated J50 intermolecular eigenstates to compute molecular constants and transition intensities without requiring explicit diagonalization of the full rotational/intermolecular vibrational Hamiltonian of the species. The approach relies on the ability to calculate the orientation of an Eckart body-fixed frame for each point on a grid over which a J50 state is represented. That ability allows one to compute vibrational matrix elements of operators referred to the Eckart axes while working with J50 eigenstates obtained in an entirely different body-fixed frame. Generally excellent agreement is found between the Eckart results and those obtained by others via diagonalization of the full rotational/intermolecular vibrational Hamiltonian. Finally, a general prescription for the construction of an efficient rovibrational basis from J50 solutions in a convenient body-fixed frame is presented. © 2001 American Institute of Physics. @DOI: 10.1063/1.1331617#