Photodissociation of interstellar ArH+
LERMA and UMR 8112, Observatoire de Paris,
place J. Janssen,
2 Fachbereich C, Physikalische und Theoretische Chemie, Bergische Universität Wuppertal, Gaußstrasse 20, 42097 Wuppertal, Germany
3 LERMA and UMR 8112, Observatoire de Paris, place J. Janssen, 92190 Meudon, France
Accepted: 5 April 2014
Aims. Following the recent detection of 36ArH+ in the Crab nebula spectrum , we have computed the photodissociation rate of ArH+ in order to constrain the physical processes at work in this environment.
Methods. Photodissociation cross-sections of ArH+ were computed in an ab initio approach that includes an explicit account of spin–orbit coupling.
Results. We report the photodissociation cross-section of ArH+ as a function of wavelength. Photodissociation probabilities are derived for different impinging radiation fields. The photodissociation probability for a very small unshielded cloud surrounded on all sides by the standard unshielded InterStellar Radiation Field (ISRF) model is equal to 9.9 × 10-12 s-1 and 1.9 × 10-9 s-1 in the Crab nebula conditions. The dependence on the visual extinction is obtained by using the Meudon photon-dominated region (PDR) code, and corresponding analytical fits are provided.
Conclusions. These data will help to produce a realistic chemical network to interpret the observations. Photodissociation of ArH+ is found to be moderate, and the presence of this molecular ion mainly depends on the molecular fraction.
Key words: astrochemistry / ISM: molecules / photon-dominated region (PDR)
© ESO, 2014