Two- and three-photon double ionization of helium by soft x-ray free-electron laser pulses. (5th March 2019)

• Record Type: Journal Article
• Authors: Shimada, Hiroyuki; Komatsu, Kazma; Komatsubara, Wataru; Mizuno, Tomoya; Miyake, Soichiro; Minemoto, Shinichirou; Sakai, Hirofumi; Majima, Takuya; Owada, Shigeki; Togashi, Tadashi; Yabashi, Makina; Yagishita, Akira
• Is Part Of: Journal of physics. Volume 52:Number 6(2019:Mar. 15)
• Publication Date: 2019-03-05
• Subjects: two-photon double ionization -- resonant ionization -- photoelectron angular distribution; Atoms -- Periodicals; Molecules -- Periodicals; Optics -- Periodicals; Nuclear physics -- Periodicals; 539.6
• DOI: 10.1088/1361-6455/ab0580
• Languages: English
• ISSNs: 0953-4075

Abstract

Abstract: The multiphoton double ionization of He was investigated using a soft x-ray free-electron laser (SX-FEL), in the perturbative intensity regime (<10 13 W cm −2 ). The photon energy was tuned to the transition between the 1s and 2p levels of He + ions. At this resonance energy of 40.8 eV, both sequential three-photon double ionization (S3PDI) and two-photon double ionization (2PDI) were measured by electron spectroscopy and by ion time-of-flight mass spectroscopy. We distinguished S3PDI from 2PDI by electron spectroscopy. Based on these experimental data, SX-FEL pulse-energy dependences of electron and ion yields for both S3PDI and 2PDI were discussed. The angular distribution of 2p photoelectrons emitted from He + (2p) ions in the S3PDI process was examined as an example of the simplest photoemission dynamics.