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Title: Comment on 'Partial Photoionization Cross Sections and Angular Distributions for Double Excitation of Helium up to the N=13 Threshold'

Abstract

A Comment on the Letter by A. Czasch et al. [Phys. Rev. Lett. 95, 243003 (2005)]. The authors of the Letter offer a Reply.

Authors:
 [1]
  1. LIXAM (Laboratoire associe au CNRS) Universite Paris-Sud 11 91405 Orsay (France)
Publication Date:
OSTI Identifier:
20957733
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 10; Other Information: DOI: 10.1103/PhysRevLett.98.109301; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANGULAR DISTRIBUTION; CROSS SECTIONS; EXCITATION; HELIUM; PHOTOIONIZATION

Citation Formats

Malegat, L. Comment on 'Partial Photoionization Cross Sections and Angular Distributions for Double Excitation of Helium up to the N=13 Threshold'. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.109301.
Malegat, L. Comment on 'Partial Photoionization Cross Sections and Angular Distributions for Double Excitation of Helium up to the N=13 Threshold'. United States. doi:10.1103/PHYSREVLETT.98.109301.
Malegat, L. Fri . "Comment on 'Partial Photoionization Cross Sections and Angular Distributions for Double Excitation of Helium up to the N=13 Threshold'". United States. doi:10.1103/PHYSREVLETT.98.109301.
@article{osti_20957733,
title = {Comment on 'Partial Photoionization Cross Sections and Angular Distributions for Double Excitation of Helium up to the N=13 Threshold'},
author = {Malegat, L.},
abstractNote = {A Comment on the Letter by A. Czasch et al. [Phys. Rev. Lett. 95, 243003 (2005)]. The authors of the Letter offer a Reply.},
doi = {10.1103/PHYSREVLETT.98.109301},
journal = {Physical Review Letters},
number = 10,
volume = 98,
place = {United States},
year = {Fri Mar 09 00:00:00 EST 2007},
month = {Fri Mar 09 00:00:00 EST 2007}
}
  • Partial photoionization cross sections {sigma}{sub N}(E{sub {gamma}}) and photoelectron angular distributions {beta}{sub N}(E{sub {gamma}}) were measured for the final ionic states He{sup +}(N>4) in the region between the N=8 and N=13 thresholds (E{sub {gamma}}>78.155 eV) using the cold target recoil ion momentum spectroscopy technique (COLTRIMS). Comparison of the experimental data with two independent sets of theoretical predictions reveals disagreement for the branching ratios to the various He{sub N}{sup +} states. The angular distributions just below the double ionization threshold suggest an excitation process for highly excited N states similar to the Wannier mechanism for double ionization.
  • Partial photoionization cross sections {sigma}{sub {ital n}} and photoelectron angular distributions {beta}{sub {ital n}} were measured for all possible final ionic states He{sup +}({ital n}) in the region of the double excitations {ital N}({ital K},{ital T}){sup {ital A}} up to the {ital N}=5 threshold. At a photon energy bandpass of 12 meV below the thresholds {ital N}=3,4, and 5, this level of differentiation offers the most critical assessment of the dynamics of the two-electron excitations to date. The experimental data are very well described by the most advanced theoretical calculations. Weaker double-excitation series with {ital K}={ital N}{minus}4 are clearly visiblemore » in the {beta}{sub {ital n}} data, and even previously unobserved extremely weak series members with {ital A}={minus}1 can be discerned, showing the high sensitivity of the angular resolved measurements. The shapes of the resonance-induced variations of {sigma}{sub {ital n}} or {beta}{sub {ital n}} in the double excitations below a given threshold {ital N} change radically depending on the final ionic state {ital n} but display striking similarities when comparing the satellite states with {ital n}={ital N}{minus}1 and {ital n}={ital N}{minus}2 below each threshold {ital N}. These systematic patterns may indicate a general rule for the underlying two-electron dynamics. {copyright} {ital 1996 The American Physical Society.}« less
  • No abstract prepared.
  • Relative partial photoionization cross-sections and angular distribution parameters, {beta}, have been measured for the first, I{sup +}({sup 3}P{sub 2})<-I({sup 2}P{sub 3/2}), and fourth, I{sup +}({sup 1}D{sub 2})<-I({sup 2}P{sub 3/2}), (5p){sup -1} photoelectron (PE) bands of atomic iodine, by performing angle-resolved constant-ionic-state (CIS) measurements on these PE bands in the photon energy range 11.0-23.0 eV. Three Rydberg series, two ns and one nd series, which converge to the I{sup +} {sup 3}P{sub 1} limit at 11.33 eV and four Rydberg series, two ns and two nd series, which converge to the I{sup +} {sup 1}D{sub 2} limit at 12.15 eV weremore » observed in the first PE band CIS spectra. The fourth band CIS spectrum showed structure in the 12.9-14.1eV photon energy range, which is also seen in the first band CIS spectra. This structure arises from excitation to ns and nd Rydberg states that are parts of series converging to the I{sup +} {sup 1}S{sub 0} limit we reported on earlier, as well as 5s{yields}5p excitations in the photon energy range 17.5-22.5 eV. These atomic iodine CIS spectra show reasonably good agreement with the equivalent spectra obtained for atomic bromine. The {beta}-plots for the first PE band recorded up to the I{sup +} {sup 3}P{sub 1} and I{sup +} {sup 1}D{sub 2} limits only show resonances corresponding to some of the 5p{yields}nd excitations observed in the first band CIS spectra scanned to the I{sup +} {sup 1}D{sub 2} limit (12.15 eV). These plots are interpreted in terms of an angular momentum transfer model with the positive values of {beta} obtained on resonances corresponding to parity allowed j{sub t}=1 and 3 channels and the off-resonance negative {beta} values corresponding to parity unfavored channels, where j{sub t} is the quantum number for angular momentum transfer between the molecule, and the ion and photoelectron. The {beta}-plots recorded for iodine are significantly different from those obtained for atomic bromine. Comparison of the experimental CIS spectra and {beta}-plots with available theoretical results highlights the need for higher level calculations which include factors such as configuration interaction in the initial and final states, relativistic effects including spin-orbit interaction, and autoionization via resonant Rydberg states.« less
  • Here we report a set of converged cross-section results for double photoionization of helium atoms obtained in the hyperspherical partial wave theory for equal energy sharing kinematics at 6 eV energy above threshold. The calculated cross section results are generally in excellent agreement with the absolute measured results of Doerner et al. [Phys. Rev. 57, 1074 (1998)].