Radiative association of He⁺₂ revisited

¹ Charles University in Prague, Faculty of Mathematics and Physics, Department of Chemical Physics and Optics, Ke Karlovu 3, 12116 Prague 2, Czech Republic
e-mail: lucie.augustovicova@mff.cuni.cz
² Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16010 Prague 6, Czech Republic
e-mail: vladimir.spirko@marge.uochb.cas.cz
³ Max-Planck-Institute of Astrophysics, Postfach 1371, 85741 Garching, Germany
e-mail: wpk@mpa-garching.mpg.de
⁴ Charles University in Prague, Faculty of Mathematics and Physics, Department of Chemical Physics and Optics, Ke Karlovu 3, 12116 Prague 2, Czech Republic
e-mail: pavel.soldan@mff.cuni.cz

Received: 19 December 2012
Accepted: 13 March 2013

Abstract

Aims. Rate coefficients for spontaneous and stimulated radiative association of the He⁺₂ molecular ion are presented as a function of temperature, considering the association with rotational-vibrational states of the ground X electronic state from the continuum states of the lowest three excited A,C, and E electronic states.

Methods. The rate coefficients are obtained from the cross sections for radiative association, which are calculated by solving the Schrödinger equation for bound and continuum states supported by the corresponding Born-Oppenheimer potential energy curves.

Results. The rate coefficients for the A → X spontaneous process are in excellent agreement with previous calculations. For temperatures up to about 10 000 K, the spontaneous C → X and E → X processes are dominant, exceeding the A → X rate coefficient by several orders of magnitude. Stimulation of the radiative association by black-body radiation has significant influence only on the A → X process at temperatures below 1000 K. The black-body radiation temperature would have to be well above 50 000 K in order to have any noticeable effect on the C → X and E → X processes.