Photoabsorption spectrum of helium trimer cation-Theoretical modeling

Abstract

The photoabsorption spectrum of He+3 is calculated for two semiempirical models of intracluster interactions and compared with available experimental data reported in the middle UV range [H. Haberland and B. von Issendorff, J. Chem. Phys.102, 8773 (1995)]. Nuclear delocalization effects are investigated via several approaches comprising quantum samplings using either exact or approximate (harmonic) nuclear wavefunctions, as well as classical samplings based on the Monte Carlo methodology. Good agreement with the experiment is achieved for the model by Knowles et al. , [Mol. Phys.85, 243 (1995); Knowles et al. , Mol. Phys.87, 827 (1996)] whereas the model by Calvo et al. , [J. Chem. Phys.135, 124308 (2011)] exhibits non-negligible deviations from the experiment. Predictions of far UV absorption spectrum of He+3 , for which no experimental data are presently available, are reported for both models and compared to each other as well as to the photoabsorption spectrum of He+2 . A simple semiempirical point-charge approximation for calculating transition probabilities is shown to perform well for He+3 .