Photodissociation threshold and emission with 220Â nm of icy ethene

The depletion of ethene, C2H4, dispersed in solid neon was measured upon irradiation with ultraviolet light from a synchrotron source. The threshold for the dissociation of solid ethene is wavelength 210 ± 5 nm, corresponding to energy 5.90 ± 0.13 eV. We recorded emission spectra for the transition T → N of ethene dispersed in solid neon, dinitrogen and water, excited at 220 nm; the band origins are 286.5, 289.8 and 290.0 nm, respectively. This investigation of the depletion of icy ethene with UV light enhances our understanding of its photochemistry in astronomical environments. This emission feature of solid ethene can provide a new means of identification for its observation in space.