X-Ray Absorption Spectrum of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi mathvariant="normal">N</mml:mi><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:msubsup></mml:math> Molecular Ion
Rebecka Lindblad, Ludvig Kjellsson, Rafael C. Couto, Martin Timm, Christine Bülow, Vicente Zamudio‐Bayer, Marcus Lundberg, Bernd von Issendorff, J. Tobias Lau, S. L. Sörensen, Vincenzo Carravetta, Hans Ågren, Jan‐Erik Rubensson
Abstract
The x-ray absorption spectrum of ${\mathrm{N}}_{2}^{+}$ in the K-edge region has been measured by irradiation of ions stored in a cryogenic radio frequency ion trap with synchrotron radiation. We interpret the experimental results with the help of restricted active space multiconfiguration theory. Spectroscopic constants of the $1{\ensuremath{\sigma}}_{u}^{\ensuremath{-}1}\text{ }{^{2}\mathrm{\ensuremath{\Sigma}}}_{u}^{+}$ state, and the two $1{\ensuremath{\sigma}}_{u}^{\ensuremath{-}1}3{\ensuremath{\sigma}}_{g}^{\ensuremath{-}1}1{\ensuremath{\pi}}_{g}\text{ }{^{2}\mathrm{\ensuremath{\Pi}}}_{u}$ states are determined from the measurements. The charge of the ground state together with spin coupling involving several open shells give rise to double excitations and configuration mixing, and a complete breakdown of the orbital picture for higher lying core-excited states.