Ortho and parahydrogen in interstellar material.
Abstract
The ortho/para molecular hydrogen ratio in the interstellar medium is considered. It is shown that the ortho/para ratio will be 3:1 in practically all chemical reactions, even at relatively low temperatures. Two examples of exothermic processes that will result in the formation of a 3:1 ortho:para ratio, corresponding to a high-temperature equilibrium, are examined: H2 formation via three-body or surface recombination and catalytic recombination involving electrons and H(-) ions. Gas-phase scrambling ion reactions are also discussed, and it is suggested that virtually all the H2 equilibrated via scrambling reactions involving H(+) and H3(+) ions should exist as parahydrogen in the J 0 quantum state. Arguments are given that deuterium cannot interfere with the long scrambling chain that results in parahydrogen formation.
- Publication:
-
Zeitschrift Naturforschung Teil A
- Pub Date:
- February 1979
- DOI:
- 10.1515/zna-1979-0206
- Bibcode:
- 1979ZNatA..34..163R
- Keywords:
-
- Interstellar Gas;
- Ortho Hydrogen;
- Para Hydrogen;
- Forbidden Transitions;
- Hydrogen Clouds;
- Thermodynamic Equilibrium;
- Astrophysics;
- Interstellar Molecules;
- Interstellar Molecules:Molecular Hydrogen