Rovibrational states of H-3(+). Part 1: The energy region below 9000 cm(-1) and modelling of the non-adiabatic effects

This group's variational method for computing rovibrational energies using hyperspherical coordinates and harmonics has been applied to all H-3(+) states below 13 000 cm(-1) (J less than or equal to 10) for which accurate energies based on a submicrohartre accuracy potential energy surface have been obtained. A comparison with a recent comprehensive compilation of experimental data below 9 000 cm(-1) shows deviations of up to 1.2 cm(-1). First it is shown that these deviations exert a systematic influence on the vibrational band but depend to a much lesser extent on rotational excitation. Then the remaining discrepancies can be attributed to the neglect of nonadiabatic effects, for which a useful correction formula based on ab initio results is obtained. The scatter in individual bands can thus be reduced to similar to0.1 cm(-1) such that these corrected results are consistent with the accuracy of the potential energy surface itself.