A 1H and 2H nuclear magnetic resonance study of amorphous ices at 77 K

Abstract

The 2H quadrupole coupling constants (QCC) of deuteriated high-density amorphous (hda) ice and low-density amorphous (lda) ice were measured to be 226.6 and 218.6 kHz with asymmetry parameters (η) 0.106 and 0.104, respectively, at 77 K. Correlations of the QCC’s with near-neighbor O–O distances in the crystalline phases of ice imply near-neighbor O–O distances of 2.84 and 2.79 Å in high- and low-density amorphous ice, respectively, compared with values of 2.79 and 2.77 Å for cubic ice (Ic) and hexagonal ice (Ih). The 1H second moment for hda ice of 37.5 G2 can be understood in terms of a short water interproton distance of 1.565 Å and the greater density of hda ice with respect to ice Ih. The 1H spin-lattice relaxation times at 77 K for hda ice and lda ice at 124 and 773 s are much shorter than the value found for the crystalline ices. It is suggested that the T1 parameter may be useful in characterizing different amorphous ice phases.