Infra-red and Raman spectra of single crystals of ice

Abstract

In this paper a brief account is given of one of the main results of an investigation on the infra-red and Raman spectra of single crystals of ice carried out recently a the University of Michigan. The first aim was to see whether infra-red analyse could be used to discriminate between various proposals which have been pu forward for the positions of the hydrogen atoms in the hexagonal crystal lattic formed by the oxygen atoms. The second objective was to obtain a complete interpretation of the vibration spectrum of ice between 50 and 10000 cm - . Nothing will be said about the latter problem, since it is too complex to be discussed satisfactorily in a short paper. The infra-red spectrum of water vapour stretches from 0·7 cm -1 to well beyond 17000 cm -1 and it has been interpreted in great detail. The general explanation is shown in table 6. In the same table, the main features of the infra-red spectrum c ice are described. As might be expected, the very extended pure rotation line spectrum of the vapour is replaced by a relatively small number of bands, which arise from the hindered rotation and translation of the water molecules in ice (intermolecular vibrations). That the water molecule preserves its individuality i seen from the fact that the values of the intra-molecular fundamentals are ged only slightly in value in going from the vapour to the solid state, i. e. v 2 1595 to 1640 cm -1 and v 3 from 3755 to 3250 cm -1 . The third fundamental ( v 1 ) ry weak in absorption but strong in the Raman spectrum, examination of h shows that it has changed from 3651 cm -1 in the vapour to 3143 cm -1 in the state. Such changes are characteristic of molecules which become hydrogen-ded in the condensed phase, viz. a lowering of the stretching frequencies ( v 1 v 3 ) bout 10% and a similar increase in the deformation frequency ( v 2 ). In this the increase in the deformation frequency appears to be very small (2·5%), this may well be due to changes in certain anharmonic and interaction con-ts in going from the vapour to the solid state.