THE TEMPERATURE-DEPENDENT SPECTRA OF ALPHA-NITROGEN AND BETA-NITROGEN ICE WITH APPLICATION TO TRITON

We present measurements of the temperature dependence of the near-infrared spectra of α and β nitrogen ice, measured in transmission in 1-cm-thick samples. Our 0.9-cm-1 resolution spectra of β ice reveal that the 4650 cm-1 (2.15 μm) hand is a complex, temperature-dependent absorption, composed of at least two components. For lower temperature α ice, our spectra show a complex, temperature-dependent pattern involving several weak features in addition to the strong, narrow band we attribute to a double phonon transition. We apply our results in modeling telescopic spectra of Triton and conclude that the spectral data are consistent with a surface composed predominantly of β nitrogen ice at temperatures between 35.6 and 41 K, in the form of grains of order 1 cm or larger in size or in the form of a surface glaze with a depth of at least 6 cm. © 1993 by Academic Press, Inc.