Two mechanisms able to induce variations in the interstellar D/H ratio are analyzed: i) In diffuse or low density media the radiation pressure mechanism induced by UV stellar fluxes shifts the deuterium population with respect to the hydrogen one. This mechanism appears to be very sensitive to temperature gradients and to ionization effects. ii) In dense media, the deuterium abundance can be enhanced because of the large photodissociation rate of HD by UV fluxes compared to that of H2 (shielding of H2). A comparison between the probabilities to observe a given D/H ratio on a given line of sight shows that the unperturbed D/H ratio should be 2 to 2.5 × 10-5 in the nearby interstellar medium and not 1.5 × 10-5 as commonly thought before. Finally we note that it is not surprising to observe significant variations of the D/H ratio in the immediate vicinity of the Sun if the hypothesis of the presence of a dense core near the solar system is adopted.
No takes yet. Share an insight, caveat, or question.
Bruston et al. (1981) studied this question.