Using block diagonalization to determine dissociating autoionizing states: Application to N₂H, and the outlook for SH

¹ Department of Physics and Nuclear Engineering, United States Military Academy, West Point, NY 10996, USA
² Laboratoire Univers et Particules de Montpellier, UMR 5299, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier, France
³ Department of Physics, Lehigh University, 16 Memorial Dr. E, Bethlehem, PA 18015, USA

^a e-mail: david.kashinski@usma.edu
^b e-mail: dahbia.talbi@univ-montp2.fr
^c e-mail: aph2@lehigh.edu

Published online: 29 January 2015

Abstract

We describe our implementation of the block diagonalization method for calculating the potential surfaces necessary to treat dissociative recombination (DR) of electrons with N₂H⁺. Using the methodology we have developed over the past few years, we performed multi-reference, configuration interaction calculations for N₂H⁺ and N₂H with a large active space using the GAMESS electronic structure code. We treated both linear and bent geometries of the molecules, with N₂ fixed at its equilibrium separation. Because of the strong Rydberg-valence coupling in N₂H, it is essential to isolate the appropriate dissociating, autoionizing states. Our procedure requires only modest additional effort beyond the standard methodology. The results indicate that the crossing between the dissociating neutral curve and the initial ion potential is not favorably located for DR, even if the molecule bends. The present calculations thereby confirm our earlier results for linear N₂H and reinforce the conclusion that the direct mechanism for DR is likely to be inefficient. We also describe interesting features of our preliminary calculations on SH.