International Workshop on Atomic Interactions in Laser Fields - Abstracts
M.D. Havey, S.B. Bayram, A. Sieradzan
Physics Department, Old Dominion University, Norfolk, VA 23529
An outstanding problem in experimental atomic spectroscopy is determination of oscillator strengths for allowed or forbidden radiative transitions. Matrix elements for such transitions bear on a wide range of fundamental problems, ranging from analysis of parity violation measurements in atoms, to determination of long-range interatomic interactions important for cold atom collisions. Generally, it is difficult to make oscillator strength or lifetime measurements with precision better than 1% or so. However, recent advances in measurement techniques have permitted precise (~10-3) determination of resonance line oscillator strengths in the alkali atoms. In this paper we describe new approaches to determination of atomic matrix elements or connections between them. Experimental results can take the form of sum rules related to the vector and scalar transition probabilities. The sum rules are illustrated by results oftwo-photon, two-color studies of polarization dependent excitation spectra of the 3s2S1/2→3p2Pj→5s 2S1/2 transition in Na and the 5s2S1/2→5p2Pj→8s 2S1/2 transition in Rb. In addition, we present preliminary data on the relative transition matrix elements for the 6s2S1/2→6p2Pj transitions and the oscillator strengths of the 6s2S1/2→7p2Pj transition in Cs. These are determined through a novel approach; polarization-dependent Rayleigh or Raman scattering off the ground level. In each of these approaches, the amplitude for the nonresonant processes depends normally on contributions from many intermediate states, even though often only a few ofthese significantly contribute. Interferences as a function of the spectral location of virtual levels for the process produce a set of zeros in the scattering amplitude. For Rayleigh scattering in the spectral vicinity of a ns2S1/2→n'p2Pj transition in an alkali atom, the location of the zero depends to an excellent approximation only on the oscillator strength for the transition, and for the resonance line. Measurements in the vicinity of the zero allow its location to be inferred with excellent precision. Then the very well-determined resonance line strength then can serve as a fiducial value by which to determine the oscillator strength for other principal series transitions.
Research supported by the National Science Foundation and the U.S. Civilian Research and Development Foundation.