title: Multiple ionization of oxygen studied by coincident measurement.
abstract: We experimentally study double and triple ionization of oxygen using a reaction microscope. The kinetic energy releases (KERs) and angular distributions are obtained through coincidentally measuring the ionic fragments of doubly or triply charged parent ions. The pathway O(2+)2 ? O (+) O(+)?proceeds through some excited electronic states. The KERs exhibit definite structures independent of the laser intensity and the pulse duration. However, the angular distribution of coincident O(+) reflects the symmetry of the highest occupied molecular orbital (HOMO) only for few-cycle laser pulses at low intensity. The pathways O(2+) 2 --> O(2+) +O and O(3+) 2 --> O(2+) + O(+) occur through some repulsive states. The KERs show a single broad peak and decrease with increasing the pulse duration. The decrease of KER comes from the stretch of the internuclear distance in intense laser fields.
authors.affiliation: Department of Physics, Peking University, Beijing 100871, People's Republic of China.
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Wu
authors.forename: Chengyin
authors.initials: C
authors.lastname: Wu
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Liu
authors.forename: Yunquan
authors.initials: Y
authors.lastname: Liu
authors.forename: Yongkai
authors.initials: Y
authors.lastname: Deng
authors.forename: Qihuang
authors.initials: Q
authors.lastname: Gong
mesh_terms: D007477:Ions / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D012031:Refractometry / Q000379:methods*
chemical_list: D007477:Ions; D010100:Oxygen