NON-BOLTZMANN VIBRATIONAL DISTRIBUTIONS IN HOMONUCLEAR DIATOMIC-MOLECULES AND IONS

We investigate the fates and population densities of the vibrationally excited homonuclear diatomic molecules H-2/H-2(+), C-2/C-2(+) and O-2 /O-2(+) in interstellar conditions using photochemical kinetic models. We find that the population distribution of vibrationally excited H-2 (+) resembles the nascent distribution from the cosmic ray ionization of H-2 under several cloud conditions. We predict that density of H-2( +)(v) could exceed that of H-2(v) under certain cloud conditions. Base d on this we present a synthetic spectrum of the quadrupole-allowed in frared emission from H-2(+)(v). Our results for H-2(v) are in accord w ith those of previous workers. The vibrationally excited states of C-2 and O-2 show abundances on the order of 10(-4) of the ground state. W e emphasize that these populations are controlled by reaction dynamics and photochemical kinetics, and do not resemble those of the local th ermodynamic equilibrium (LTE), Preliminary models of the C-2(+)(v) and O-2(+)(v) chemistry show that the vibrational distributions will some what resemble the nascent distributions of the reactions which create them. Further experimental or theoretical studies of the dynamics of t hese reactions are necessary before quantitative predictions can be ma de.