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Title: Strong-field ionization of lithium

Abstract

We report photoelectron energy spectra, momentum, and angular distributions for the strong-field single ionization of lithium by 30-fs laser pulses. For peak intensities between 10{sup 11} and 10{sup 14} W/cm{sup 2} at a central wavelength of 785 nm, the classical over-the-barrier intensity was reached well inside the multiphoton regime. The complete vector momenta of the ionization fragments were recorded by a reaction microscope with a magneto-optically trapped target (MOTREMI). On the theoretical side, the time-dependent Schroedinger equation was solved by two independent methods seeking the solution directly on a radial grid. Distinct differences between the results of both calculations and also in comparison with experiment point to a high sensitivity of this reaction with respect to small details, particularly in the description of the Li{sup +} core.

Authors:
; ; ; ; ;  [1]; ;  [2];  [3];  [4]
  1. Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, DE-69117 Heidelberg (Germany)
  2. Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200 (Australia)
  3. Institute of Nuclear Physics, Moscow State University, Moscow RU-119991 (Russian Federation)
  4. Department of Physics and Astronomy, Drake University, Des Moines, Iowa 50311 (United States)
Publication Date:
OSTI Identifier:
21537180
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 83; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevA.83.023413; (c) 2011 American Institute of Physics
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ANGULAR DISTRIBUTION; COMPARATIVE EVALUATIONS; ENERGY SPECTRA; IONIZATION; LASER RADIATION; LASERS; LITHIUM; LITHIUM IONS; MATHEMATICAL SOLUTIONS; MICROSCOPES; MULTI-PHOTON PROCESSES; PEAKS; PULSES; SCHROEDINGER EQUATION; TIME DEPENDENCE; WAVELENGTHS; ALKALI METALS; CHARGED PARTICLES; DIFFERENTIAL EQUATIONS; DISTRIBUTION; ELECTROMAGNETIC RADIATION; ELEMENTS; EQUATIONS; EVALUATION; IONS; METALS; PARTIAL DIFFERENTIAL EQUATIONS; RADIATIONS; SPECTRA; WAVE EQUATIONS

Citation Formats

Schuricke, Michael, Zhu Ganjun, Steinmann, Jochen, Simeonidis, Konstantinos, Dorn, Alexander, Ullrich, Joachim, Ivanov, Igor, Kheifets, Anatoli, Grum-Grzhimailo, Alexei N., and Bartschat, Klaus. Strong-field ionization of lithium. United States: N. p., 2011. Web. doi:10.1103/PHYSREVA.83.023413.
Schuricke, Michael, Zhu Ganjun, Steinmann, Jochen, Simeonidis, Konstantinos, Dorn, Alexander, Ullrich, Joachim, Ivanov, Igor, Kheifets, Anatoli, Grum-Grzhimailo, Alexei N., & Bartschat, Klaus. Strong-field ionization of lithium. United States. doi:10.1103/PHYSREVA.83.023413.
Schuricke, Michael, Zhu Ganjun, Steinmann, Jochen, Simeonidis, Konstantinos, Dorn, Alexander, Ullrich, Joachim, Ivanov, Igor, Kheifets, Anatoli, Grum-Grzhimailo, Alexei N., and Bartschat, Klaus. 2011. "Strong-field ionization of lithium". United States. doi:10.1103/PHYSREVA.83.023413.
@article{osti_21537180,
title = {Strong-field ionization of lithium},
author = {Schuricke, Michael and Zhu Ganjun and Steinmann, Jochen and Simeonidis, Konstantinos and Dorn, Alexander and Ullrich, Joachim and Ivanov, Igor and Kheifets, Anatoli and Grum-Grzhimailo, Alexei N. and Bartschat, Klaus},
abstractNote = {We report photoelectron energy spectra, momentum, and angular distributions for the strong-field single ionization of lithium by 30-fs laser pulses. For peak intensities between 10{sup 11} and 10{sup 14} W/cm{sup 2} at a central wavelength of 785 nm, the classical over-the-barrier intensity was reached well inside the multiphoton regime. The complete vector momenta of the ionization fragments were recorded by a reaction microscope with a magneto-optically trapped target (MOTREMI). On the theoretical side, the time-dependent Schroedinger equation was solved by two independent methods seeking the solution directly on a radial grid. Distinct differences between the results of both calculations and also in comparison with experiment point to a high sensitivity of this reaction with respect to small details, particularly in the description of the Li{sup +} core.},
doi = {10.1103/PHYSREVA.83.023413},
journal = {Physical Review. A},
number = 2,
volume = 83,
place = {United States},
year = 2011,
month = 2
}
  • The modification in the dynamics of the electron-impact ionization process of a Li{sup +} ion due to an intense linearly polarized monochromatic laser field (n{gamma}e,2e) is studied theoretically using coplanar geometry. Significant laser modifications are noted due to multiphoton effects both in the shape and magnitude of the triple-differential cross sections (TDCSs) with respect to the field-free (FF) situation. The net effect of the laser field is to suppress the FF cross sections in the zeroth-order approximation [Coulomb-Volkov (CV)] of the ejected electron wave function, while in the first order [modified Coulomb-Volkov (MCV)], the TDCSs are found to be enhancedmore » or suppressed depending on the kinematics of the process. The strong FF recoil dominance for the (e,2e) process of an ionic target at low incident energy is destroyed in the presence of the laser field. The FF binary-to-recoil ratio changes remarkably in the presence of the laser field, particularly at low incident energies. The difference between the multiphoton CV and the FF results indicates that for the ionic target, the Kroll-Watson sum rule does not hold well at the present energy range in contrast to the neutral atom (He) case. The TDCSs are found to be quite sensitive with respect to the initial phase of the laser field, particularly at higher incident energies. A significant qualitative difference is noted in the multiphoton ejected energy distribution (double-differential cross sections) between the CV and the MCV models. Variation of the TDCSs with respect to the laser phase is also studied.« 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.
  • 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
  • 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.