Eur. Phys. J. D (2014) 68: 83
https://doi.org/10.1140/epjd/e2014-40703-9

Regular Article

Doubly excited states of molecular hydrogen by scattered electron-ion coincidence measurements^*

¹ Department of Physics, Rikkyo University, Nishi-Ikebukuro, Toshimaku, 171-8501 Tokyo, Japan
² Department of Physics, Toho University, Miyama, Funabashi, 274-8510 Chiba, Japan

^a e-mail: karin@rikkyo.ac.jp

Received: 11 November 2013
Received in final form: 10 February 2014
Published online: 23 April 2014

Abstract

Electron energy-loss spectroscopy and electron-ion coincidence techniques were used to determine the total generalized oscillator strength distribution (GOSD) of molecular hydrogen (H₂) under 200 eV incident electron energy at a scattering angle of 6 degree. Ionic GOSDs were obtained for each formed ion at each energy-loss value and were determined by scattered electron-ion coincidence measurements. The total and partial ionic GOSDs of H₂ were compared with the OOSDs from the experimental results of both photon and fast-electron impacts. We observed auto-ionization induced by excitation to the optically forbidden Q₁ ¹Σ⁺_g(1) state near 28 eV. Additionally, the non-ionic GOSD, defined as the difference between the total GOSD and the total ionic GOSD, was determined. From the non-ionic GOSD, neutral dissociation from excitation to the forbidden Q₁ ¹Σ⁺_g(1) state near 28 eV and the Q₂ series near 35 eV were identified.