15min:
STRUCTURE OF COLD, MIXED PARAHYDROGEN-DEUTERIUM CLUSTERS.

RUSSELL SLITER AND ANDREY F. VILESOV, Department of Chemistry, University of Southern California, Los Angeles, CA 90089.

Vibrational spectra of para-H2 molecules in clusters consisting of para-H2 or para-H2/D2 seeded in He have been obtained using coherent anti-Stokes Raman spectroscopy. The Q1(0) line of para-H2, obtained upon expansion of neat para-H2/D2, exhibits a high frequency vibrational shift of about 2.6 cm-1 with change of D2 concentration from 0 to 98%. This shift is assigned to a decrease of the para-H2 vibron band width in mixed clusters, similar to that previously observed in bulk H2/D2 solid. 1% para-H2/D2 clusters in He are liquid and show a much smaller shift of about 0.5 cm-1 and indicate phase separation into a predominantly D2 core and H2 shell. The onset of phase separation in para-H2/D2 mixtures is predicted at approximately 3 K providing further evidence of super-cooled liquid hydrogen clusters previously studied.