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APS » Journals » Phys. Rev. Lett. » Volume 73 » Issue 9
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Phys. Rev. Lett. 73, 1227–1230 (1994)

Precision Measurement of Strong Field Double Ionization of Helium

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B. Walker1, B. Sheehy1, L. F. DiMauro2, P. Agostini2, K. J. Schafer3, and K. C. Kulander3,4
1Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973
2Service Recherches sur les Surfaces et l'Irradiation de la Matière, Centre d'Etudes de Saclay, 91191 Gif Sur Yvette, France
3Theoretical, Atomic and Molecular Physics, Lawrence Livermore National Laboratory, Livermore, California 94551
4Joint Institute for Laboratory Astrophysics, University of Colorado, Boulder, Colorado 80309

Received 27 April 1994; published in the issue dated 29 August 1994

The production of He+ and He2+ by a 160 fs, 780 nm laser has been measured over an unprecedented 12 orders of magnitude in counting range. Enhanced double electron emission, called nonsequential (NS) ionization, was observed over an intensity range where the single ionization dynamics is evolving from multiphoton to pure tunneling. The NS yield is found to scale with the ac-tunneling rate for the neutral, even when tunneling is not the dominant ionization pathway. A rescattering mechanism fails to predict the observed NS threshold or magnitude.

© 1994 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.73.1227
DOI:
10.1103/PhysRevLett.73.1227
PACS:
32.80.Rm, 31.90.+s, 32.80.Fb
 
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