The infrared (IR) spectra, including
spectral intensities, of solid
hydrocarbons are of interest to astrochemists and astronomers for
the relevance of these compounds to surface chemistry in the outer
solar system and beyond. However, although the vibrational modes and
IR peak positions of many such compounds have long been studied, much
less attention has been paid to the IR intensities needed to quantify
both astronomical observations and laboratory results. Here we present
mid- and near-IR transmission spectra of a relatively little-studied
solid hydrocarbon, allene (1,2-propadiene). Spectra of both amorphous
and polycrystalline allene are shown for the first time along with
optical constants, band strengths, and absorption coefficients. We
also report a density and refractive index (670 nm) for each form
of solid allene. A radiation-chemical experiment on allene’s
formation is described, as are some applications and suggestions for
future work.