skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Magnetic-Field Induced Enhancement in the Fluorescence Yield Spectrum of Doubly Excited States in Helium

Abstract

An influence of static magnetic fields on the fluorescence yield spectrum of He in the vicinity of the N=2 thresholds has been observed. The experimental results are in excellent agreement with predictions based on multichannel quantum defect theory, and it is demonstrated that the Rydberg electron l mixing due to the diamagnetic interaction is essential for the description of the observed fluorescence yield intensity enhancement.

Authors:
; ; ;  [1];  [1];  [2];  [3];  [4];  [5];  [6];  [4];  [7];  [8]
  1. Department of Physics, Uppsala University, Box 530, S-75121 Uppsala (Sweden)
  2. (Germany)
  3. Dipartimento di Chimica, Universita di Roma La Sapienza and INSTM Unit, Piazzale Aldo Moro 5, I-00185 Rome (Italy)
  4. (Italy)
  5. Sincrotrone Trieste, I-34012 Trieste (Italy)
  6. Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Sezione Roma 1, Piazzale Aldo Moro 5, I-00185 Rome (Italy)
  7. Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008-5151 (United States)
  8. Department of Physics, Auburn University, Auburn, Alabama 36849 (United States)
Publication Date:
OSTI Identifier:
20861519
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 97; Journal Issue: 25; Other Information: DOI: 10.1103/PhysRevLett.97.253002; (c) 2006 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; ELECTRONS; FLUORESCENCE; HELIUM; MAGNETIC FIELDS; RYDBERG STATES

Citation Formats

Stroem, Magnus, Saathe, Conny, Agaaker, Marcus, Soederstroem, Johan, Rubensson, Jan-Erik, BESSY, Albert-Einstein Strasse 15, D-12489 Berlin, Stranges, Stefano, Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Sezione Roma 1, Piazzale Aldo Moro 5, I-00185 Rome, Richter, Robert, Alagia, Michele, TASC-CNR, Area Science Park, Basovizza, I-34012 Trieste, Gorczyca, T. W., and Robicheaux, F. Magnetic-Field Induced Enhancement in the Fluorescence Yield Spectrum of Doubly Excited States in Helium. United States: N. p., 2006. Web. doi:10.1103/PHYSREVLETT.97.253002.
Stroem, Magnus, Saathe, Conny, Agaaker, Marcus, Soederstroem, Johan, Rubensson, Jan-Erik, BESSY, Albert-Einstein Strasse 15, D-12489 Berlin, Stranges, Stefano, Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Sezione Roma 1, Piazzale Aldo Moro 5, I-00185 Rome, Richter, Robert, Alagia, Michele, TASC-CNR, Area Science Park, Basovizza, I-34012 Trieste, Gorczyca, T. W., & Robicheaux, F. Magnetic-Field Induced Enhancement in the Fluorescence Yield Spectrum of Doubly Excited States in Helium. United States. doi:10.1103/PHYSREVLETT.97.253002.
Stroem, Magnus, Saathe, Conny, Agaaker, Marcus, Soederstroem, Johan, Rubensson, Jan-Erik, BESSY, Albert-Einstein Strasse 15, D-12489 Berlin, Stranges, Stefano, Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Sezione Roma 1, Piazzale Aldo Moro 5, I-00185 Rome, Richter, Robert, Alagia, Michele, TASC-CNR, Area Science Park, Basovizza, I-34012 Trieste, Gorczyca, T. W., and Robicheaux, F. Fri . "Magnetic-Field Induced Enhancement in the Fluorescence Yield Spectrum of Doubly Excited States in Helium". United States. doi:10.1103/PHYSREVLETT.97.253002.
@article{osti_20861519,
title = {Magnetic-Field Induced Enhancement in the Fluorescence Yield Spectrum of Doubly Excited States in Helium},
author = {Stroem, Magnus and Saathe, Conny and Agaaker, Marcus and Soederstroem, Johan and Rubensson, Jan-Erik and BESSY, Albert-Einstein Strasse 15, D-12489 Berlin and Stranges, Stefano and Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Sezione Roma 1, Piazzale Aldo Moro 5, I-00185 Rome and Richter, Robert and Alagia, Michele and TASC-CNR, Area Science Park, Basovizza, I-34012 Trieste and Gorczyca, T. W. and Robicheaux, F.},
abstractNote = {An influence of static magnetic fields on the fluorescence yield spectrum of He in the vicinity of the N=2 thresholds has been observed. The experimental results are in excellent agreement with predictions based on multichannel quantum defect theory, and it is demonstrated that the Rydberg electron l mixing due to the diamagnetic interaction is essential for the description of the observed fluorescence yield intensity enhancement.},
doi = {10.1103/PHYSREVLETT.97.253002},
journal = {Physical Review Letters},
number = 25,
volume = 97,
place = {United States},
year = {Fri Dec 22 00:00:00 EST 2006},
month = {Fri Dec 22 00:00:00 EST 2006}
}
  • We have measured the lifetimes of {sup 1}P{sup e} (n=9-12) doubly excited states in static electric fields (1-6 kV/cm) by observing the decay of the fluorescence signal as a function of time. The effects of the field on these helium states below the second ionization threshold are twofold: their excitation becomes possible due to the Stark mixing with the optically allowed {sup 1}P{sup o} series, and their lifetime is strongly modified by the opening of the autoionization channel, not accessible in zero field. Although the electric field represents only a tiny perturbation of the atomic potential, a substantial shortening ofmore » the lifetimes below 100 ps is observed. This is the simplest quantum system where the ratio of autoionization to fluorescence decay probability can be effectively controlled by an electric field of moderate strength.« less
  • Doubly excited states in helium are calculated with many-body perturbation theory to all orders in the electron-electron interaction. A finite and numerical basis set, rotated out into the complex plane, is used. Results, for energies and widths, are presented for states with electrons in the [ital n]=2 and [ital n]=3 states. The possiblity of an accuracy of a few parts in 10[sup 6] is demonstrated. The method is equally applicable to the study of doubly excited states of many-electron systems and the extension to the corresponding relativistic procedure is straightforward.
  • The beam-foil spectrum of helium from 2050 to 3600 A has been acquired at 160-keV incident ion energy using a multiple-scan, computerized system. Eleven doubly-excited-state transitions, including two not previously observed, have been assigned, and the agreement between experimental and theoretical energy levels is excellent. The Stokes parameters as a function of foil-tilt angle have been measured for the two strongest transitions (2578 and 3013 A) from 0/sup 0/ to 80/sup 0/ in 10/sup 0/ increments and for two weaker transitions (2562 and 2818 A) at 0/sup 0/, 20/sup 0/, 40/sup 0/, and 60/sup 0/. The polarization patterns are quitemore » different from those of the helium singlets and include the first measurement of negative M/I (a Stokes parameter) at 0/sup 0/ foil tilt for helium at this energy. The lifetime of the 2578-A transition has been investigated in detail. The present result, 0.109 +- 0.004 ns, agrees with previous measurements and yields an upper limit to the autoionization width of the 2p3p /sup 3/D levels of 6 x 10/sup -6/ eV.« less
  • The double retarding potential difference method allows the detection of doubly excited states by measuring the electrons resulting from the decay of these states into ions. This is illustrated in the case of helium. (auth)
  • We present a study of the influence of the constant uniform electric field and spin-orbit interaction on the doubly excited 2l2l{sup '} resonance states of helium-like ions. The calculation is performed in the framework of the complex coordinate rotation method allowing one to obtain results both for real part of the energy (position of the resonance) and for imaginary part of the energy (related to the width of the resonance). Singlet and triplet states with angular momenta from L=0 to L=4 have been included in the calculation. Results are given for the M=0 Stark components of the Feshbach {sup 1}S{supmore » e}(1), {sup 1}P{sup o}, {sup 1}D{sup e} {sup 3}P{sup e}, {sup 3}P{sup o} resonances. We show that though spin-orbit interaction generally produces only a minor effect, in a situation where real parts of energies of singlet and triplet levels cross, the spin-orbit interaction can dramatically modify behavior of the widths of these states.« less