Inelastic neutron scattering spectra were measured for amorphous ice ${\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{D}}_2\mathrm{O}$ produced by low-temperature and low-rate vapor deposition. The data show that the deposition produced the low-density amorphous form of ice, i.e., the high-density amorphous ice observed by x-ray [A. H. Narten, C. G. Venkatesh, and S. A. Rice, J. Chem. Phys. 64, 1106 (1976)] and electron diffraction [P. Jenniskens and D. F. Blake, Science 265, 753 (1994)] under similar conditions was not detected. This result was confirmed by separate neutron diffraction experiments. Vibrational spectra of the deposited amorphous ice were dissimilar to that of ice ${\mathrm{I}}_h/{\mathrm{I}}_c$, as was believed previously.

• Received 21 March 1997

DOI:https://doi.org/10.1103/PhysRevLett.79.1869