Universal features in sequential and nonsequential two-photon double ionization of helium

Journal Article · Sun May 15 00:00:00 EDT 2011 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.83.053418· OSTI ID:21546801

Pazourek, R; Nagele, S; Persson, E; Burgdoerfer, J ^[1]; Feist, J ^[1]; Schneider, B I ^[2]; Collins, L A ^[3]

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1. Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna (Austria)
2. Office of Cyberinfrastructure/Physics Division, National Science Foundation, Arlington, Virginia 22230 (United States)
3. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

We analyze two-photon double ionization of helium in both the nonsequential (({h_bar}/2{pi}){omega}<I{sub 2}{approx_equal}54.4 eV) and sequential (({h_bar}/2{pi}){omega}>I{sub 2}) regime. We show that the energy spacing {Delta}E=E{sub 1}-E{sub 2} between the two emitted electrons provides the key parameter that controls both the energy and the angular distribution and reveals the universal features present in both the nonsequential and sequential regime. This universality, i.e., independence of ({h_bar}/2{pi}){omega}, is a manifestation of the continuity across the threshold for sequential double ionization. For all photon energies considered, the energy distribution can be described by a universal shape function that contains only the spectral and temporal information entering second-order time-dependent perturbation theory. Angular correlations and distributions are found to be more sensitive to the value of ({h_bar}/2{pi}){omega}. In particular, shake-up interferences have a large effect on the angular distribution. Energy spectra, angular distributions parametrized by the anisotropy parameters {beta}{sub j}, and total cross sections presented in this paper are obtained by fully correlated time-dependent ab initio calculations.

• OSTI ID: 21546801
• Journal Information: Physical Review. A, Vol. 83, Issue 5; Other Information: DOI: 10.1103/PhysRevA.83.053418; (c) 2011 American Institute of Physics; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ANGULAR CORRELATION
ANGULAR DISTRIBUTION
ANISOTROPY
ELECTRON EMISSION
ENERGY SPECTRA
EV RANGE
HELIUM
INTERFERENCE
IONIZATION
PERTURBATION THEORY
PHOTONS
TIME DEPENDENCE
TOTAL CROSS SECTIONS
BOSONS
CORRELATIONS
CROSS SECTIONS
DISTRIBUTION
ELEMENTARY PARTICLES
ELEMENTS
EMISSION
ENERGY RANGE
FLUIDS
GASES
MASSLESS PARTICLES
NONMETALS
RARE GASES
SPECTRA