Dielectric relaxation spectroscopy of pressure amorphized hexagonal ice shows that water’s high-density amorphous form relaxes in $\sim 1\mathrm{s}$ at 140 K and 1 GPa and that the relaxation is virtually unaffected by pressure. This indicates that the amorph is an ultraviscous liquid above 140 K, the same as would be obtained by supercooling water at 1 GPa through its ice VI phase boundary, and that the glass transition temperature is independent of pressure and close to that of amorphous solid water produced at atmospheric pressure.

• Received 15 April 2005

DOI:https://doi.org/10.1103/PhysRevLett.95.205503