Eur. Phys. J. D (2017) 71: 48
https://doi.org/10.1140/epjd/e2017-70465-7

Regular Article

Doubly excited states of molecular nitrogen by scattered electron-ion coincidence measurements

¹ Dept. of Phys., Toho University, Miyama, Funabashi, 274-8510 Chiba, Japan
² Research Center for Materials with Integrated Properties, Toho University, Miyama, Funabashi, 274-8510 Chiba, Japan

^a e-mail :karin@ph.sci.toho-u.ac.jp

Received: 22 July 2016
Received in final form: 21 November 2016
Published online: 2 March 2017

Abstract

Scattered electron-ion coincidence measurements were performed on molecular nitrogen (N₂) to study the relaxation dynamics of doubly excited states. Doubly excited states are typically so unstable that they result in either auto-ionization or a neutral dissociation. In auto-ionization, ionization and dissociation typically occur. Using a mixed-gas method, we determined the absolute values of the generalized oscillator strength (GOS) distributions using an incident electron energy of 200 eV and a scattering angle of 6°. The GOS distributions of N₂⁺ and N⁺ were determined by combining the coincidence ion signals, which revealed some doubly excited states of N₂. Since electron impact experiments can provide information on optically forbidden transitions, the contribution of optically forbidden states appears in the GOS distributions of both N₂⁺ and N⁺. We observed auto-ionization and dissociative auto-ionization induced by excitation to the optically forbidden doubly excited states in the range of 30–40 eV.