Single and double K-shell resonant photoionization and Auger decay of 1s → 2p excited states of O⁺–O⁴⁺

¹ Department of Physics, College of Science, National University of Defense Technology, Changsha Hunan 410073, PR China
e-mail: jlzeng@nudt.edu.cn
² IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240, PR China
³ Graduate school of China Academy of engineering Physics, Beijing 100193, PR China

Received: 4 May 2017
Accepted: 13 June 2017

Abstract

In this work, single and double photoionization cross sections in the vicinity of 1s → 2p resonances are investigated theoretically for quantum states belonging to the ground and first excited configurations of O⁺–O⁴⁺. R-matrix method has been employed to obtain the single ionization cross section, whereas the double ionization cross sections are obtained by the branching ratios of the direct double Auger decay to the total Auger decay. By analyzing possible double ionization pathways, we conclude that the double photoionization originates predominately from the direct double Auger decay of the K-shell resonant states. Our theoretical work diagnosed the population fraction of the quantum state prepared in a recent experiment and successfully interpreted the experimental observations on both single and double photoionization cross sections.