FORMATION OF H2+ AND ITS ISOTOPOMERS BY RADIATIVE ASSOCIATION: THE ROLE OF SHAPE AND FESHBACH RESONANCES

Abstract

The recent observations [1,2] of shape and Feshbach resonances in the high-resolution photoelectron spectra of H$_2$, HD and D$_2$ in the vicinity of the dissociation thresholds of H$_2^+$, HD$^+$ and D$_2^+$ raise questions concerning their potential role in the formation of H$_2^+$ and its isotopomers in the early universe by radiative association, a topic of astrophysical interest~[3]._x000d_ Close-coupling calculations for the cross sections of the reactions_x000d_ \begin{align} _x000d_ \text{H}^+ + \text{H} &\to \text{H}_2^+ + h\nu \\_x000d_ \text{H}^+ + \text{D} &\to \text{HD}^+ + h\nu \\_x000d_ \text{D}^+ + \text{H} &\to \text{HD}^+ + h\nu \\_x000d_ \text{D}^+ + \text{D} &\to \text{D}_2^+ + h\nu,_x000d_ \end{align}_x000d_ will be presented which take into account nonadiabatic couplings involving rovibronic and hyperfine interactions, as well as relativistic and radiative corrections._x000d_ The calculated energies and widths will be compared with the experimental results of Ref. [1,2] for H$_2^+$ and new data for HD$^+$ and D$_2^+$. The effect of the resonances on the radiative association rate coefficients will be discussed, also in comparison with earlier studies [4]._x000d_ _x000d_ \noindent [1] M. Beyer and F. Merkt, \textit{Phys. Rev. Lett.} \textbf{116}, 093001 (2016)._x000d_ _x000d_ \noindent [2] M. Beyer and F. Merkt, \textit{J. Mol. Spectrosc.} \textbf{330}, 147 (2016)._x000d_ _x000d_ \noindent [3] Molecule formation in dust-poor environments, J. F. Babb and K. P. Kirby, in "The molecular astrophysics of stars and galaxies", T. W. Hartquist and D. A. Williams, eds., Oxford University Press, Oxford, 1998, pp. 11-34._x000d_ _x000d_ \noindent [4] D. E. Ramaker and J. M. Peek, \textit{Phys. Rev. A} \textbf{13}, 58 (1976).