A mean field approximation is used to calculate the librational properties of dgr;hyphen;phase molecular oxygen monolayers on graphite at temperatures 0le;Tle;20 K. The frequencies of the two libron modes are found to occur at 35.07 and 60.28 cmminus;1. The libron specific heat and the rms orientational fluctuations of the O2molecules about equilibrium are also determined. It is found that the contribution of zerohyphen;point orientational fluctuations to librational behavior is large. The molecules exhibit well defined small angle librational motion at low temperatures and there is no evidence of an orientational orderndash;disorder phase transition prior to melting at 25.6 K.
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