The interaction of H-2 with water ice by neutron scattering: Rotation and translation

The inelastic neutron scattering from H-2 in D2O ice at energy transfers th at correspond to rotation-translation are presented. Both the first energy gain and the energy loss peaks are observed. The position of the peaks show s that the H-2 molecules execute nearly free rotation. The translational (r ecoil) contribution to the band positions as well as their widths can be fi t by free translation with the molecule having an effective mass of about 1 .7 M-0 where M-0 is the mass of H-2. The experimental results are compared to the available computer simulations. (C) 1999 American Institute of Physi cs. [S0021-9606(99)50215-8].