VIBRATIONAL-MODES OF AMORPHOUS ICE - BENDING MODE FREQUENCIES FOR ISOTOPICALLY DECOUPLED H2O AND HOD AT 90-K

The bending mode for the water molecule in amorphous ice has been investigated by, (a) comparing the FR-IR spectra of amorphous ice with that of cubic ice in the 1600 cm-1 region, and (b) observation of new features in this region that accompany the incorporation of the isotopomers H2O and HOD into amorphous D2O (or H2O) ice. The comparison with cubic ice is interesting because it reveals the major decrease in the bending mode oscillator strength that apparently accompanies crystallization and also allows a tentative identification of the v2 peak frequency of intermolecularly coupled H2O ice (1693 cm-). Subtraction techniques have produced the more reliable v2 frequencies of 1711 cm-1 an 1480/1490 cm-1 for H2O decoupled in amorphous D2O and HOP decoupled in H2O/D2O, respectively. Based on these values of the bending mode frequencies, an assignment has been made of the components of the H2O band complex in the OH stretching mode region. The resulting assignment is consistent with the published assignment of the decoupled isotopomer frequencies of cubic ice and adds a further element of credibility to that important assignment. © 1990.