Title: Quantum dynamics of the temporary capture of light atoms by superfluid helium nanodroplets at very low collision energies (1–13 meV): the case of the hydrogen atom and its isotopes

Authors: M. Sternberg, S. K. Gray and M. González

DOI: 10.1039/d5cp01498k

Abstract: The capture dynamics of a H atom and isotopic variants [D, T and Q (hypothetical isotope of mass equal
to four times the mass of H)] by a superfluid helium nanodroplet (HeND) has been investigated
theoretically. The HeND (T = 0.37 K) is (4He)N=400 and a mean field quantum hybrid approach [TDDFT
(helium) + quantum wave packet (H, D, T or Q)] at zero angular momentum, is used to explore a rather
wide range of very low initial kinetic energies (Ek,0: 10–150 K). The analysis of the capture mechanism
shows the existence of a dynamical barrier and a dynamical minimum that play key roles to understand
the time evolution of the capture, especially the former property. In general, the H atom shows a different
behavior from the other isotopes, with the behavior of T and Q being very similar to each other and
the D atom behaving in between H and T. Besides, it is worth noting that, in principle, at the very low
initial kinetic energies considered only ‘‘short’’ and ‘‘long’’ lived atom—HeND collision complexes are
formed, i.e., in the atom-helium nanodroplet collision only the temporary capture of the atom takes
place. The different behaviors observed have been interpreted considering the faster motion of the H
atom when colliding with (4He)N=400 and the more quantum character of the H behavior both due to its
significantly lower mass. As far as we know, this is the first quantum dynamics study carried out on the
collision of light atoms with HeNDs at very low energies.