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Title: Comment on 'Strong-field ionization of laser-irradiated light homonuclear diatomic molecules: A generalized strong-field approximation-combination of atomic orbitals model'

Abstract

V. I. Usachenko and S.-I. Chu [Phys. Rev. A, 71, 063410 (2005)] discuss the molecular strong-field approximation in the velocity gauge formulation and indicate that some of our earlier velocity gauge calculations are inaccurate. Here we comment on the results of Usachenko and Chu. First, we show that the molecular orbitals used by Usachenko and Chu do not have the correct symmetry, and second, that it is an oversimplification to describe the molecular orbitals in terms of just a single linear combination of two atomic orbitals. Finally, some values for the generalized Bessel function are given for comparison.

Authors:
;  [1]
  1. Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C (Denmark)
Publication Date:
OSTI Identifier:
20787178
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 73; Journal Issue: 4; Other Information: DOI: 10.1103/PhysRevA.73.047401; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; APPROXIMATIONS; BESSEL FUNCTIONS; COMPARATIVE EVALUATIONS; IRRADIATION; LASER RADIATION; MOLECULES; PHOTOIONIZATION; PHOTON-MOLECULE COLLISIONS; SYMMETRY; VISIBLE RADIATION

Citation Formats

Kjeldsen, Thomas Kim, and Madsen, Lars Bojer. Comment on 'Strong-field ionization of laser-irradiated light homonuclear diatomic molecules: A generalized strong-field approximation-combination of atomic orbitals model'. United States: N. p., 2006. Web. doi:10.1103/PHYSREVA.73.0.
Kjeldsen, Thomas Kim, & Madsen, Lars Bojer. Comment on 'Strong-field ionization of laser-irradiated light homonuclear diatomic molecules: A generalized strong-field approximation-combination of atomic orbitals model'. United States. doi:10.1103/PHYSREVA.73.0.
Kjeldsen, Thomas Kim, and Madsen, Lars Bojer. Sat . "Comment on 'Strong-field ionization of laser-irradiated light homonuclear diatomic molecules: A generalized strong-field approximation-combination of atomic orbitals model'". United States. doi:10.1103/PHYSREVA.73.0.
@article{osti_20787178,
title = {Comment on 'Strong-field ionization of laser-irradiated light homonuclear diatomic molecules: A generalized strong-field approximation-combination of atomic orbitals model'},
author = {Kjeldsen, Thomas Kim and Madsen, Lars Bojer},
abstractNote = {V. I. Usachenko and S.-I. Chu [Phys. Rev. A, 71, 063410 (2005)] discuss the molecular strong-field approximation in the velocity gauge formulation and indicate that some of our earlier velocity gauge calculations are inaccurate. Here we comment on the results of Usachenko and Chu. First, we show that the molecular orbitals used by Usachenko and Chu do not have the correct symmetry, and second, that it is an oversimplification to describe the molecular orbitals in terms of just a single linear combination of two atomic orbitals. Finally, some values for the generalized Bessel function are given for comparison.},
doi = {10.1103/PHYSREVA.73.0},
journal = {Physical Review. A},
number = 4,
volume = 73,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}
  • We acknowledge the criticism of the preceding Comment related to imperfect composition of our model 3{sigma}{sub g} molecular state [V. I. Usachenko and S.-I. Chu, Phys. Rev. A 71, 063410 (2005)]. However, we cannot agree with the authors suggesting this critique also as an irrefutable argument and evidence in support and justification of their opposite and incorrect (viz. inconsistent with relevant experiment) orientation dependence of N{sub 2} ionization rate calculated within the velocity gauge version of molecular strong-field approximation. We demonstrate that appropriately composed 3{sigma}{sub g} state (modified according to the Comment's critique) rather confirm the alternative calculation [A. Jaron-Becker,more » A. Becker, and F. H. M. Faisal, Phys. Rev. A 69, 023410 (2004)], which suggests correct orientation dependence of N{sub 2} ionization, contrary to respective results of the Comment's authors applying the same approach and procedure of 3{sigma}{sub g} composition.« less
  • The strong-field ionization in a number of light homonuclear diatomic molecules (N{sub 2}, O{sub 2}, and H{sub 2}) irradiated by an intense laser field of low fundamental frequency {omega}<<I{sub p} is considered theoretically and studied numerically compared to their 'companion' atoms, having nearly identical ionization potential I{sub p}. The background applied strong-field approach is based on using the S-matrix formalism of conventional strong-field approximation supplemented by the standard linear combination of atomic orbitals and molecular orbitals method utilized for approximate analytical reproduction of the two-centered wave function of an initial molecular bound state. Accordingly, the ionization of a diatomic moleculemore » is described as a quantum-mechanical superposition (intramolecular interference) of contributions from ionization amplitudes corresponding to photoelectron emission from two atomic centers separated by equilibrium internuclear distance. Besides the bonding (or antibonding) symmetry of the highest occupied molecular orbitals (HOMO) corresponding to the outermost molecular valence shell, its spatial configuration and predominant orientation with respect to the internuclear axis and polarization of incident laser field also proved to be of substantial importance and, thus, are taken into equally detailed consideration. Moreover, wherever appropriate, the comparable contributions from other (inner) molecular valence shells of a larger binding energy (closest to that of HOMO, but of different bonding symmetry and spatial configuration) are additionally taken into account. The related results for calculated differential and/or integral molecular ionization rates, molecular photoelectron spectra, and angular distributions are fairly well consistent with available experimental data and, in particular, provide one with a transparent physical interpretation of the nature and origin of high suppression in ionization of the O{sub 2} molecule (as compared to its companion Xe atom) as well as no suppression in ionization of N{sub 2} molecules (as compared to its companion Ar atom)« less
  • We investigate high-order above-threshold ionization (HATI) of diatomic molecules having different symmetries by an elliptically polarized laser field using the modified molecular strong-field approximation. The yields of high-energy electrons contributing to the plateau region of the photoelectron spectra strongly depend on the employed ellipticity. This is more pronounced if the major axis of the polarization ellipse is parallel or perpendicular to the molecular axis and at the end of the high-energy plateau. For the O{sub 2} molecule (characterized by {pi}{sub g} symmetry) the maximum yield is observed for some value of the ellipticity {epsilon} different from zero. On the othermore » hand, in the same circumstances, the N{sub 2} molecule ({sigma}{sub g}) behaves as an atom, i.e., the yield is maximum for {epsilon}=0. These characteristics of the photoelectron spectra remain valid in a wide region of the molecular orientations and laser peak intensities. The symmetry properties of the molecular HATI spectra are considered in detail: by changing the molecular orientation one or other type of the symmetry emerges or disappears. Presenting differential ionization spectra in the ionized electron energy-emission angle plane we have observed similar interference effects as in the HATI spectra governed by a linearly polarized field.« less
  • We present a detailed comparison of strong-field ionization of diatomic molecules and their companion atoms with nearly equal ionization potentials. We perform calculations in the length and velocity gauge formulations of the molecular strong-field approximation and with the molecular tunneling theory, and in both cases we consider effects of nuclear motion. A comparison of our results with experimental data shows that the length gauge strong-field approximation gives the most reliable predictions.