Spin-driven structural effects in alkali doped He-4 clusters from quantum calculations

In this paper, we carry out variational Monte Carlo and diffusion Monte Carlo DMC calculations for Li2(1Sigma+g)(4He)N and Li2(3Sigma+u)(4He)N with N up to 30 and discuss in detail the results of our computations. After a comparison between our DMC energies with the “exact” discrete variable representation values for the species with one 4He, in order to test the quality of our computations at 0 K, we analyze the structural features of the whole range of doped clusters. We find that both species reside on the droplet surface, but that their orientation is spin driven, i.e., the singlet molecule is perpendicular and the triplet one is parallel to the droplet’s surface. We have also computed quantum vibrational relaxation rates for both dimers in collision with a single 4He and we find them to differ by orders of magnitude at the estimated surface temperature. Our results therefore confirm the findings from a great number of experimental data present in the current literature and provide one of the first attempts at giving an accurate, fully quantum picture for the nanoscopic properties of alkali dimers in 4He clusters.