The resonantly enhanced multiphoton ionization of atomic hydrogen is studied for the case of four-photon ionization (three-photon resonant). The time-dependent probabilities, the shape of the resonance profile at different intensities, and the nonlinear index are computed for coherent light at frequencies around the resonance (365 nm). The systematic dependence of the cross section as a function of the principal quantum number of the resonant state (as this tends towards the Rydberg states) is investigated at zero detuning. The probabilities of absorption of one photon more than necessary for the four-photon ionization process (resonantly enhanced above-threshold ionization) is computed and the relevant branching ratios are examined. Then it is shown that the effect of the spatio-temporal structures of the laser pulse is to red shift the maximum of the resonance profile, whereas that of an ideal chaotic light is to blue shift and broaden the resonance peak. The shape, shift, and width of the profile resulting from both these effects are in very fair agreement with the experimental ones.The resonantly enhanced multiphoton ionization of atomic hydrogen is studied for the case of four-photon ionization (three-photon resonant). The time-dependent probabilities, the shape of the resonance profile at different intensities, and the nonlinear index are computed for coherent light at frequencies around the resonance (365 nm). The systematic dependence of the cross section as a function of the principal quantum number of the resonant state (as this tends towards the Rydberg states) is investigated at zero detuning. The probabilities of absorption of one photon more than necessary for the four-photon ionization process (resonantly enhanced above-threshold ionization) is computed and the relevant branching ratios are examined. Then it is shown that the effect of the spatio-temporal structures of the laser pulse is to red shift the maximum of the resonance profile, whereas that of an ideal chaotic light is to blue shift and broaden the resonance peak. The shape, shift, and width of the profile resulting from both these effects are in very fair agreement with the experimental ones.

Physical Review AJun 1, 198815 citations

Theoretical Investigation on the REMPI Processes of Two-Level System

Zhifeng Cui

Based on the time-dependent density-matrix equations of two-level system,the analytical formule of the resonance-enhanced multiphoton ionization(REMPI) probabilities of atom were obtained under the resonant and near-resonant condition.Furthermore,for the(2+1) REMPI of oxygen atom with the 2p~34p as resonant state,the dependence of the ionization probability on laser intensity,pulse width and resonance detuning was discussed.At the same time,the relation of the saturation condition of REMPI to the laser intensity and the pulse width was derived.Under the near-resonant condition,the analytical results showed that the ionization probability decreased with the increase of resonance detuning with the fixed laser intensity and pulse width,and the ionization probability increased with the increase of laser intensity at the fixed resonance detuning and tended to become saturation when laser intensity was high enough.Under the resonant condition,the amplitude of the ionization probability increased rapidly with the pulse width when laser intensity increased.Based on the time-dependent density-matrix equations of two-level system,the analytical formule of the resonance-enhanced multiphoton ionization(REMPI) probabilities of atom were obtained under the resonant and near-resonant condition.Furthermore,for the(2+1) REMPI of oxygen atom with the 2p~34p as resonant state,the dependence of the ionization probability on laser intensity,pulse width and resonance detuning was discussed.At the same time,the relation of the saturation condition of REMPI to the laser intensity and the pulse width was derived.Under the near-resonant condition,the analytical results showed that the ionization probability decreased with the increase of resonance detuning with the fixed laser intensity and pulse width,and the ionization probability increased with the increase of laser intensity at the fixed resonance detuning and tended to become saturation when laser intensity was high enough.Under the resonant condition,the amplitude of the ionization probability increased rapidly with the pulse width when laser intensity increased.

Chinese Journal of LasersJan 1, 20051 citation

Influence of Multiphoton Resonance on the Multiphoton Ionization Process

G. A. Delone, Nikolai B. Delone

JETPLNov 1, 19693 citations

Photon correlation effects in resonant multiphoton ionization

S. N. Dixit, P. Lambropoulos

The effect of photon correlations on two- and three-photon ionization via two near-resonant levels is discussed in terms of the resolvent-operator formalism. It is shown that under certain circumstances the ionization probability for a chaotic light can be enhanced by a factor larger than $N!$ compared to the ionization probability for a coherent light. The dependence of this enhancement factor on the interaction time, the average intensity, the detunings of the photon frequency from the near-resonant levels, and the separation between the two near-resonant levels is discussed.The effect of photon correlations on two- and three-photon ionization via two near-resonant levels is discussed in terms of the resolvent-operator formalism. It is shown that under certain circumstances the ionization probability for a chaotic light can be enhanced by a factor larger than $N!$ compared to the ionization probability for a coherent light. The dependence of this enhancement factor on the interaction time, the average intensity, the detunings of the photon frequency from the near-resonant levels, and the separation between the two near-resonant levels is discussed.

Physical Review AJan 1, 198027 citations

Resonance Effects in Multiphoton Ionization

Niels J. Kylstra

Springer eBooksJan 1, 19974 citations

N!

compared to the ionization probability for a coherent light. The dependence of this enhancement factor on the interaction time, the average intensity, the detunings of the photon frequency from the near-resonant levels, and the separation between the two near-resonant levels is discussed.