Resonant multiphoton ionization of a caesium atomic beam by a tunable wavelength Q-switched neodymium laser

J. Morellec

В. В. Суран

Nilam Shrestha

Bernard Held, G. Mainfray, C. Manus +2 more

The narrow spectral bandwith (0.4 \AA{}) of a Nd-glass laser was tuned over a range of 40 \AA{} to populate selectively the $6f$ level of cesium atoms. The resulting variation of the multiphoton ionization probability was investigated as a function of the laser wavelength.

R.G. Evans, Peter C. Thonemann

G. Petite, J. Morellec, Didier Normand

This paper studies the resonant multiphoton ionization (RMPI) phenomenon, in the case of caesium atoms interacting with the intense field of a neodymium-Glass laser. In the first part, we present a recent theory of RMPI, in a simplified form in order to obtain the main informations on the physics of RMPI. Then we present two experiments of RMPI : four-photon ionization of the caesium atom in its ground state, with a three-photon resonance on the 6F level and three-photon ionization of the caesium atom is its 62P3/2 state with a two-photon resonance on the 12F level. In the first experiment, the internal structure of the resonant transition is resolved, enabling us to point out and analyse the important effect of pulse shapes and focusing conditions on our experimental results, which are discussed in detail. We also give some new interpretations of results published previously [1]. In the second experiment, we measure the 12F fine structure — which is found to be (0.016 ± 0.008) cm-1 — and show that we have reached the limits imposed by the Doppler effect. These experimental results are in good agreement with the theoretical predictions suggesting that the physical picture given of RMPI by recent works on this subject is satisfactory.