Charge Transfer as a Diagnostic of Excitation Dynamics in a MOT

G. Veshapidze, M. L. Trachy, H. A. Camp, M. A. Gearba, M. H. Shah, X. Flechard, H. U. Jang, H. Nguyen, J. Blieck, R. Bredy, C. W. Fehrenbach, B. D. DePaola
James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS, USA

The technique of model-independent, direct measurement of the excited state fraction of various states in a cold target by means of Q-value spectroscopy is presented. For this, the charge transfer reaction in ion-cold atom collisions is used and the momentum "kick", experienced by the recoil ion is measured using standard "recoil ion momentum spectroscopy" techniques. The momentum kick experienced by the recoil ion after charge transfer is related to the difference between initial and final binding energies of the transferred electron. Therefore, once the cross-section for each capture channel has been determined, measurements of recoil ion momentum spectra allow one to identify the relative fractions of the initial states occupied by electron in the cold target just before the charge transfer. Example applications of this technique are presented for measuring the excited state fraction in a MOT as a function of trapping laser intensity and detuning, and for measuring the evolution of populations in a 3-level ladder system undergoing coherent excitation via stimulated Raman adiabatic passage (STIRAP).

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.

Presented at ISIAC, August 2007 in Crete, Greece.

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