Indirect Ultraviolet Photodesorption from CO:N2 Binary Ices -- an Efficient Grain-gas Process

摘要: Ultraviolet (UV) ice photodesorption is an important non-thermal desorption pathway in many interstellar environments that has been invoked to explain observations of cold molecules disks, clouds, and cloud cores. Systematic laboratory studies the rates, between 7 14 eV, from CO:N2 binary ices, have performed at DESIRS vacuum UV beamline synchrotron facility SOLEIL. The spectral analysis demonstrates process indirect, i.e., induced by a photon absorption sub-surface molecular layers, while only surface are actually desorbing. spectra CO N2 ices therefore depend on dominant species layer, which implies efficiency energy dependence dramatically different for mixed layered compared with pure ices. In particular, thin (1-2 ML) layer top will effectively quench photodesorption, enhancing factor few (compared ices) when exposed typical dark field, may help distributions N2H+ This indirect mechanism also small amounts complex organics environments.