High-density amorphous ice. IV. Raman spectrum of the uncoupled O–H and O–D oscillators

Abstract

The Raman spectrum of the uncoupled O–H and O–D stretching vibrations of HDO dissolved in H2O high-density amorphous ice, that was made from ice Ih, has been measured at 12 K for the sample as recovered at 77 K and after heating it at 5 K min−1 from 12 K to, successively, 80, 90, 100, ..., 170 K and annealing there for 5 min. The distribution of hydrogen-bonded O–H--O and O–D--O distances was estimated by using an experimental curve of the O–H stretching frequency as a function of the O--O distance in ice VII, as suitably adjusted using the frequency in ice I. The most probable bond length, as estimated from the peak frequency, is 2.83 Å, which is 0.08 Å longer than the length in ice I, and the distribution of bond lengths has a width at half-height of 0.19 Å. When the sample was heated to 80, 90, 100, 110, and 120 K in succession, the peak frequency and the width at half-height, as measured at 12 K, decreased by amounts that corresponded to a decrease of the most probable distance from 2.83 to 2.76 Å and a decrease of the width at half-height from 0.19 to 0.09 Å. The phase produced at 120 K is a low-density amorph, and it changes little after heating to 130 and 140 K. After heating to 150 K it changes to ice Ic, whose peak frequency implies an O--O distance of 2.75 Å.