Formation of negative ions in the interstellar medium by dissociative electron attachment to the H$_2$CN molecule*

The methylene amidogen radical (H$_2$CN) was first discovered, in 1962 by Cochran $et\ al.$ [1], and since then it has received considerable attention from both experimentalists and theoreticians. It is considered an important intermediate in the combustion of nitramine propellants and proposed to play a role in extraterrestrial atmospheres. It was detected in interstellar clouds in 1994 [2], and its dissociative electron attachment (DEA) process may be responsible for the formation of the CN$^-$ and the H$^-$ negative ions: $e^-$+H$_2$CN $\to$ CN$^-$ + H$_2$; $e^-$+H$_2$CN $\to$ H$^-$ + HCN. We report here the results of our ab initio quantum chemical studies of the geometrical and electronic structure of the methylene amidogen and and its negative ion H$_2$CN$^-$ in the theoretical of DEA in H$_2$CN. The scattering calculations are carried out using the complex Kohn variational method. The nuclear dynamics, including dissociation, will later be treated using the MCTDH code [3] with a three-dimensional potential energy surface, in which the distance of CN is kept frozen. [1] E. L. Cochran $et\ al.$ J. Chem. Phys., 1962, 36, 1938. [2] M. Ohishi $et\ al.$, Astrophys. J., 1994, 427, L51. [3] G. A. Worth $et\ al.$, MCTDH package, Version 8.4