Quantum solvent states and rovibrational spectra of small doped 3He clusters through the full-configuration-interaction nuclear orbital approach: The „ (3He)N–Cl2„(X) case (N<4)

Abstract

A full-configuration-interaction nuclear orbital treatment has been recently developed as a benchmark quantum-chemistry-like method to study small doped 3He clusters M. P. de Lara-Castells et al., 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 M. P. de Lara-Castells et al., J. Chem. Phys. 131, 194101 2009 , and apply the method to the 3He N–Cl2 X case, using both a semiempirical 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 localized 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 configurations. 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 rovibrational 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.