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.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.

Journal de physiqueJan 1, 197954 citations

Multiphoton Ionization of Atoms (REVIEW)

Didier Normand, Jürgen Reif, J. Morellec

Jan 1, 19840 citations

Theory of Multiphoton Ionization of Atoms

Yves Gontier, M. Trahin

Elsevier eBooksJan 1, 19842 citations

Resonant enhanced multiphoton ionization studies in atomic oxygen

S. N. Dixit, Deborah A. Levin, B. V. McKoy

In this paper we analyze two-photon-resonant three-photon ionization of atomic oxygen via the 2 ${\mathit{p}}^{3}$ ${(}^{4}$ S\ifmmode^\circ\else\textdegree\fi{}) ${\mathit{np}}^{3}$ ${\mathit{P}}_{0}$ ,1,2, and the 2 ${\mathit{p}}^{3}$ ${(}^{4}$ S\ifmmode^\circ\else\textdegree\fi{})nf $^{3}$ ${\mathit{F}}_{2}$ ,3,4 states. The various atomic parameters required for calculating the resonant enhanced multiphoton ionization (REMPI) probabilities are obtained using quantum-defect theory. The infinite sums over nonresonant states are truncated at a finite number of terms. Our calculated two-photon excitation cross sections agree well with the results of other recent calculations and of experimental measurements. The photoionization cross section is calculated for various electron kinetic energies. The REMPI dynamics is analyzed by solving the density-matrix equations. This framework consistently takes into account the effects of saturation and ac Stark shifts. REMPI probability is seen to be quite sensitive to the initial detuning, the intensity, and the particular resonant state accessed. The photoionization cross sections also imply that due to the rapid falloff of the cross section, two-color REMPI schemes with a lower-frequency ionizing photon would increase the effective REMPI probability.In this paper we analyze two-photon-resonant three-photon ionization of atomic oxygen via the 2${\mathit{p}}^{3}$${(}^{4}$S\ifmmode^\circ\else\textdegree\fi{})${\mathit{np}}^{3}$${\mathit{P}}_{0}$,1,2, and the 2${\mathit{p}}^{3}$${(}^{4}$S\ifmmode^\circ\else\textdegree\fi{})nf $^{3}$${\mathit{F}}_{2}$,3,4 states. The various atomic parameters required for calculating the resonant enhanced multiphoton ionization (REMPI) probabilities are obtained using quantum-defect theory. The infinite sums over nonresonant states are truncated at a finite number of terms. Our calculated two-photon excitation cross sections agree well with the results of other recent calculations and of experimental measurements. The photoionization cross section is calculated for various electron kinetic energies. The REMPI dynamics is analyzed by solving the density-matrix equations. This framework consistently takes into account the effects of saturation and ac Stark shifts. REMPI probability is seen to be quite sensitive to the initial detuning, the intensity, and the particular resonant state accessed. The photoionization cross sections also imply that due to the rapid falloff of the cross section, two-color REMPI schemes with a lower-frequency ionizing photon would increase the effective REMPI probability.

Physical Review AJun 1, 198821 citations

In this paper we analyze two-photon-resonant three-photon ionization of atomic oxygen via the 2

{\mathit{p}}^{3}

{(}^{4}

S\ifmmode^\circ\else\textdegree\fi{})

{\mathit{np}}^{3}

{\mathit{P}}_{0}

,1,2, and the 2

{\mathit{p}}^{3}

{(}^{4}

S\ifmmode^\circ\else\textdegree\fi{})nf

^{3}

{\mathit{F}}_{2}

,3,4 states. The various atomic parameters required for calculating the resonant enhanced multiphoton ionization (REMPI) probabilities are obtained using quantum-defect theory. The infinite sums over nonresonant states are truncated at a finite number of terms. Our calculated two-photon excitation cross sections agree well with the results of other recent calculations and of experimental measurements. The photoionization cross section is calculated for various electron kinetic energies. The REMPI dynamics is analyzed by solving the density-matrix equations. This framework consistently takes into account the effects of saturation and ac Stark shifts. REMPI probability is seen to be quite sensitive to the initial detuning, the intensity, and the particular resonant state accessed. The photoionization cross sections also imply that due to the rapid falloff of the cross section, two-color REMPI schemes with a lower-frequency ionizing photon would increase the effective REMPI probability.