The Raman spectrum of the uncoupled Ondash;H and Ondash;D stretching vibrations of HDO dissolved in H2O highhyphen;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 Kthinsp;minminus;1from 12 K to, successively, 80, 90, 100, ..., 170 K and annealing there for 5 min. The distribution of hydrogenhyphen;bonded Ondash;Hhyphen;hyphen;O and Ondash;Dhyphen;hyphen;O distances was estimated by using an experimental curve of the Ondash;H stretching frequency as a function of the Ohyphen;hyphen;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 Aring;, which is 0.08 Aring; longer than the length in ice I, and the distribution of bond lengths has a width at halfhyphen;height of 0.19 Aring;. When the sample was heated to 80, 90, 100, 110, and 120 K in succession, the peak frequency and the width at halfhyphen;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 Aring; and a decrease of the width at halfhyphen;height from 0.19 to 0.09 Aring;. The phase produced at 120 K is a lowhyphen;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 Ohyphen;hyphen;O distance of 2.75 Aring;.
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