Infrared Spectra and Optical Constants of Astronomical Ices: II. Ethane
  and Ethylene
  Infrared spectroscopic observations have established the presence of
hydrocarbon ices on Pluto and other TNOs, but the abundances of such molecules
cannot be deduced without accurate optical constants (n, k) and reference
spectra. In this paper we present our recent measurements of near- and
mid-infrared optical constants for ethane (C$_2$H$_6$) and ethylene
(C$_2$H$_4$) in multiple ice phases and at multiple temperatures. As in our
recent work on acetylene (C$_2$H$_2$), we also report new measurements of the
index of refraction of each ice at 670 nm. Comparisons are made to earlier work
where possible, and electronic versions of our new results are made available.
