Absence of Intense Laser Population Trapping in Rydberg States of Highly Charged Rare Gas Ions

E. Wells, R.R. Jones
(Department of Physics, University of Virginia, Charlottesville, VA 22904-4714)
I. Ben-Itzhak
(Department of Physics, Kansas State University, Manhattan, KS 66506)

The branching ratio for production of Rydberg ions, Aⁿ⁺, to ions A⁽ⁿ⁺¹⁾, during intense laser ionization of rare gas atoms, has been measured as a function of laser intensity and polarization. Previous measurements¹ in Xe and Kr showed that highly excited Rydberg ions, created via transient resonances during intense laser ionization of these species, could survive the laser field strengths required to produce noble gas ions, provided that the ionizing laser pulse duration is shorter than the Kepler period of the Rydberg electron. Highly stripped Rydberg ions have been considered as a potential gain medium for an X-ray laser or amplifier². Currently, using 100 fs, 790 nm laser pulses, singly and double charged Rydberg ions are observed in Xe. In Kr and Ar, however, only singly charged Rydberg ions are seen. We propose that the absence of highly-charged Rydberg ions may be due to pulsed field-ionization of the Rydberg electron in the gradient of the pondermotive potential of the focused laser beam.

References:

1) R.R. Jones, et al., Phys. Rev. A 47, R49 (1993).
2) R.B. Vrijen and L.D. Noordam, J. Opt. Soc. Am. B 13, 189 (1996).

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division,
Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Submitted to DAMOP 2002, May 2002 in Williamsburg, VA.

 

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