Water deuteration and ortho-to-para nuclear spin ratio of H2 in molecular clouds formed via the accumulation of HI gas

摘要: We investigate the water deuteration ratio and ortho-to-para nuclear spin of H2 (OPR(H2)) during formation early evolution a molecular cloud, following scenario that accretion flows sweep accumulate HI gas to form clouds. follow physical post-shock materials using one-dimensional shock model, with post-processing gas-ice chemistry simulations. This approach allows us study OPR(H2) without an arbitrary assumption concerning initial abundances, including OPR(H2). When conversion hydrogen into is almost complete, already much smaller than statistical value three due in phase. As accumulates, decreases non-equilibrium manner. find ice can be deuterium-poor at end its main stage compared vapor observed vicinity low-mass protostars where likely sublimated. If this case, enrichment deuterium should mostly occur somewhat later evolutionary stages star formation, i.e., cold prestellar/protostellar cores. The mechanism suppress cloud cycle photodissociation reformation ice, which efficiently removes from chemistry. removal efficiency depends on pathway ice. plays minor role