I fail to see how ultraviolet radiation would produce deuterium. Since deuterium is hydrogen plus a neutron, and ultraviolet radiation is not a neutron stream.>>>

Deuterium emits a telltale spectral fingerprint in the ultraviolet energy range. An important, but often-overlooked process is radiation-induced isotope enrichment. In studies of electron-beam induced processing of ice surfaces, they have measured large isotope effects leading to enrichment of deuterium in the condensed phase. Clearly UV can and does enrich hydroden to produce large amounts of deuterium.