Instability of Small Deuterium Clusters in Superfluid Helium near the λ Point

Abstract

We present the results of quasielastic small-angle neutron scattering study of deuterium clusters immersed in superfluid 4 He. Diffraction intensities exhibit a very strong change in a character at temperatures above 1.95 K but below the λ point. They are compared with calculations based on the assumption that clusters with different sizes and structures as well as single molecules may contribute in a to- tal diffraction pattern with their particular varied relative weights. We have found that small clusters with N< 300 molecules intensively decrease in size and a big abun- dance of free deuterium molecules form inside superfluid 4 He below the λ point that evidences in favor of instability of smallest deuterium clusters at 1.95 <T <2.17 K while larger clusters undergo only minor growth.