Quantum solvent states and ro-vibrational spectra of small doped

Abstract

A Full-Con¯guration-Interaction Nuclear Orbital treatment has been recently developed as a bench- mark Quantum-Chemistry-like method to study small doped 3He clusters [J. Chem. Phys. 125, 221101 (2006)]. Our objective in this paper is to extend our previous study on (3He)N-Cl2(B) clusters, using an enhanced implementation that allows employing very large one-particle basis sets [J. Chem. Phys. 131, 174110 (2009)], and apply the method to the (3He)N-Cl2(X) case, using both a semi-empirical T-shaped and an ab initio He-dopant potential with minima at both T-shaped and linear conformations. Calculations of the ground and low-lying excited solvent states stress the key role played by the anisotropy of the He-dopant interaction in determining the global energies and the structuring of the 3He atoms around the dopant. Whereas 3He atoms are local- ized in a broad belt around the molecular axis in ground-state N-sized complexes with N=1¡3, irrespective of using the T-shaped or the ab initio He-dopant potential function, the dopant species becomes fully coated by just four 3He atoms when the He-dopant potential also has a minimum at linear con¯gurations. However, excited solvent states with a central ring-type clustering of the host molecule are found to be very close in energy with the ground state by using the ab initio potential function. A microscopic analysis of this behavior is provided. Additional simulations of the molecular ro-vibrational Raman spectra, also including excited solvent states, provide further insights into the importance of proper modeling the anisotropy of the He-dopant interaction in these weakly bound systems and of taking into account the low-lying excitations. Keywords: doped helium clusters, full-con¯guration-interaction, quantum-chemistry-like, hard-core interac- tion, ro-vibrational Raman spectroscopy