Theoretical determination of the vibrational levels of NH3+ and its isotopomers

Céline Léonard (1) , S. Carter (2) , N. C. Handy (1) , P. J. Knowles (3)

1 Department of Chemistry
2 Department of Chemistry
3 School of Chemistry

The vibrational levels associated with the electronic ground state X2A2'' of NH3+ have been determined up to 5000 cm-1 by perturbation and variational calculations with full dimensionality of the molecule. For the variational part a new version ofMULTIMODE was used which uses the ab initio electronic energy and its first derivative to define the potential energy function. These quantities were generated by the B97-1 density functional and RCCSD(T) approaches. For ND3+ , ND2H+ and NDH2+ the vibrational levels were calculated only by perturbation theory. The rotational constants for all the isotopomers were determined and the first transition dipole moments for NH3+ and ND3+ were plotted. A critical comparison of the perturbation and variational techniques suggests a possible further modification to the MULTIMODE algorithm for large systems.

Domaines: Chimie théorique et/ou physique

Céline Léonard, S. Carter, N. C. Handy, P. J. Knowles. Theoretical determination of the vibrational levels of NH3+ and its isotopomers. Molecular Physics, 2001, 99 (16), pp.1135--1346. ⟨10.1080/00268970110052928⟩. ⟨hal-00720907⟩