The intermolecular potential of He–OCS

Abstract

The dynamics of molecules trapped inside or bound to the surface of liquid helium droplets is a most exciting new development. As an aid toward the understanding of the spectrum of OCS in liquid helium, we report the intermolecular potential between He and OCS studied by ab initio calculations and high-resolution microwave spectroscopy. The potential is found to have three minima, corresponding to a T-shaped configuration for the global minimum and secondary minima at either end of the OCS molecule. The three lowest calculated bound states are loosely localized in each of the minima, with the ground state being T-shaped. Ten rotational transitions of the ground state are observed in the frequency region 1.5–45.0 GHz. Comparison of theory with experiment shows good agreement. The agreement improves substantially if the calculated He–OCS intermolecular potential is made uniformly 10% deeper and the He–OCS separation is reduced by 0.05 Å.

OCS in small para-hydrogen clusters: Energetics and structure with N=1–8 complexed hydrogen molecules

“…In this case we have used the He-OCS interaction potential of ref. [34] and the He-He potential proposed by Aziz and co-workers [35]. P 12 (φ) describes here the pair distribution of para-hydrogen (helium) in the ring located in the global minimum region of the OCS-(p-H 2 ) (OCS-He) interaction.…”

Structure and Spectroscopy of Doped Helium Clusters Using Quantum Monte Carlo Techniques

“…The increase of the moment of inertia measured in helium droplets 18 leads to a ratio B/B 0 ∼ 37 % that is nevertheless similar to the ratio for SF 6 . Because the anisotropy of the OCS-He potential 20 is very pronounced, we expect that adiabatic following will also be strong for this system, even though the rotor is somewhat faster than SF 6 . Path integral computation of the local superfluid and nonsuperfluid solvation densities show that the energetic criterion for adiabatic following is indeed fulfilled.…”

Potential generation and path‐integral Monte Carlo in study of microscopic superfluidity

“…[50] For some systems, such as COAH 2 , [35][36][37] CCSDT(Q) [51] with triple and quadruple excitations is needed to make the calculated spectroscopic transitions agree with experiment. For larger systems, for example, HCCCNAHe, [52] OCSAHe, [53,54] and OCSAH 2 , [55] less expensive many-body perturbation theory at the nth order [56] with n5224 can also be used. If higher accuracy is pursued, for example, H 2 OAH 2 , [57] methods that include explicit correlation, for example, CCSD(T)-R12, [58,59] can be used.…”