Ab initio calculation of the rotation-vibration energy levels of H-3(+) and its isotopomers to spectroscopic accuracy

Surfaces are fitted to the Born-Oppenheimer potential energy, electronic re lativistic correction and adiabatic correction data calculated ab initio by Cencek et al. [J. Chem. Phys. 108, 2831 (1998)]. These surfaces are used i n calculations of the rotation-vibration energy levels of H-3(+), H2D+, D2H +, and D-3(+). Nonadiabatic corrections to the Born-Oppenheimer approximati on are introduced following models developed for diatomics which involve th e use of isotopomer independent scaled vibrational reduced masses. It is sh own that for triatomics this approach leads to an extra term in the nuclear motion Hamiltonian. Our final calculations reproduce the known spectroscop ic data for H-3(+) and its isotopomers to within a few hundredths of a cm(- 1). (C) 1999 American Institute of Physics. [S0021-9606(99)00811-9].