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

Resonance ionization of atoms

Alexey E. Kazakov, Vyacheslav P. Makarov, Mikhail Vladimirovich Fedorov

Journal of Experimental and Theoretical PhysicsJan 1, 19762 citations

Competition between spontaneous radiation and ionization in the process of resonance enhanced multi-photon ionization

Guiyin Zhang, Haiping Li, Haiming Zheng +1 more

Photo-ionization probability is an important factor in the practical use of resonance enhanced multiphoton ionization (REMPI). To a certain experimental condition, it depends on the competition between spontaneous radiation and ionization of the excited particles. In this work, we investigate the influence of laser resonance detuning, Rabi frequency and ionization rate on spontaneous radiation and ionization in the process of REMPI with the theory of density matrix equation. A model of three energy level system is adopted. It is found that the spontaneous radiation and ionization probability increase with the decrease of laser resonance detuning. They get to the maximum when resonance detuning equals zero. The line width of spontaneous emission will decrease with the increase of ionization rate due to the competition between spontaneous radiation and ionization. In addition, the spontaneous radiation and ionization probability increase with Rabi frequency until gets to saturation. Laser resonance detuning has no influence on the saturation value. It only influences the Rabi frequency for saturation. If Rabi frequency increases further after saturation, the spontaneous radiation will decrease because of the phenomena of energy level splitting in strong laser field. Now that resonant absorption and large laser intensity can increase the ionization probability greatly, so we must select suitable laser frequency and large laser intensity in the practical use of REMPI, in order to get optimum detection result.Photo-ionization probability is an important factor in the practical use of resonance enhanced multiphoton ionization (REMPI). To a certain experimental condition, it depends on the competition between spontaneous radiation and ionization of the excited particles. In this work, we investigate the influence of laser resonance detuning, Rabi frequency and ionization rate on spontaneous radiation and ionization in the process of REMPI with the theory of density matrix equation. A model of three energy level system is adopted. It is found that the spontaneous radiation and ionization probability increase with the decrease of laser resonance detuning. They get to the maximum when resonance detuning equals zero. The line width of spontaneous emission will decrease with the increase of ionization rate due to the competition between spontaneous radiation and ionization. In addition, the spontaneous radiation and ionization probability increase with Rabi frequency until gets to saturation. Laser resonance detuning has no influence on the saturation value. It only influences the Rabi frequency for saturation. If Rabi frequency increases further after saturation, the spontaneous radiation will decrease because of the phenomena of energy level splitting in strong laser field. Now that resonant absorption and large laser intensity can increase the ionization probability greatly, so we must select suitable laser frequency and large laser intensity in the practical use of REMPI, in order to get optimum detection result.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIENov 29, 20120 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.