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Rotational energy relaxation quantum dynamics of a diatomic molecule in a superfluid helium nanodroplet and study of the hydrogen isotopes case

M. Blancafort-Jorquera, A. Vila, M. González. 
Phys. Chem. Chem. Phys.21 (2019) 21007.

Populations of the (j=0, mj=0) (solid lines) and (j=2, mj=0) (dashed lines) rotational states of molecules, as a function of time.

The rotational energy relaxation (RER) of a molecule X2(j, mj) in a 4He superfluid nanodroplet [HeND; T=0.37 K] was studied using a hybrid quantum dynamics approach proposed by us. This is the first theoretical study about RER in HeNDs and here several isotopes of H2 were examined. The structure of the HeND does not change during the RER, which takes place according to a cascade mechanism and mj is conserved. The lifetime of an excited rotational state (≈1.0-7.6 ns) increases when Be increases, increases, and decreases (above N=100 He atoms there is a small influence of on the lifetime). The analysis of the influence of the coupling between the – j-2 rotational states and the X2 angular velocity on the lifetime was helpful to interpret the results. We hope that the present study will encourage more studies on RER in HeND, a basic, interesting and difficult to study phenomenon about which we still know very little.