FOURFOLD CLUSTERS OF ROVIBRATIONAL ENERGIES IN H2PO STUDIED WITH AN AB INITIO POTENTIAL ENERGY FUNCTION

摘要

We report here an ab initio investigation of the cluster effect (i.e., the formation of four-member groups of nearly degenerate rotation-vibration energy levels at higher J and K-a values) in the H2Po molecule. The potential energy function has been calculated ab initio for a total of 143 molecular geometries by means of the CCSD(T) method, using an averaged relativistic effective potential for Po in conjunction with a newly optimized basis set. The values of the potential energy function obtained cover the region up to around 5000 cm(-1) above the equilibrium energy. On the basis of the ab initio potential, the rotation-vibration energies of (H2Po)-Po-209 have been calculated with the MORBID (Morse oscillator rigid bender internal dynamics) Hamiltonian and computer program. In particular, we have calculated the rotational energy manifolds for J less than or equal to 40 in the vibrational ground state. We find that the formation of fourfold clusters in H2Po is very similar to that in H2Te. (C) 1997 Academic Press. [References: 31]