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RIS and competing processes in high concentration atomic vapors

Rainer Wunderlich, M. G. Payne, W. R. Garrett

Published Aug 1, 1986• 3 citations
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Abstract

Three-photon ionization of Na out of the 4d two-photon state is discussed. Results from an atomic beam and an atomic vapor in a heat pipe are compared. The 4d ionization in the vapor was a factor of 10/sup 4/ smaller than in the beam. Absorption in the vapor was less than concentration arguments might suggest. This reduction is explained by very fast processes which dump the resonant state into lower levels and by a process which suppresses the two-photon excitation at high concentrations. Experimental evidence of these processes was observed as strong infrared and ultraviolet emission in the forward direction corresponding to the 4d ..-->.. 4p and 4p ..-->.. 3s transition, respectively. 11 refs., 5 figs.

Related papers

Two-photon excitation of dense sodium vapor near the nd /sup 2/D/sub 5/2,//sub //sub 3/2/ (n = 3, 4, 5) levels: Na/sub 2/ 1 /sup 3//Sigma//sup +//sub g//yields/1 /sup 3//Sigma//sup +//sub u/ excimer emission

Stanley J. Bajic, R. N. Compton, John A. D. Stockdale +1 more

Laser excitation and ionization processes in dense (1--10 Torr) sodium vapor have been studied for laser wavelengths near the two-photon allowed nd /sup 2/D(n = 3, 4, 5) and ns /sup 2/S(n = 4, 5, 6) states. In particular, the 1 /sup 3//Sigma//sup +//sub g//yields/1 /sup 3//Sigma//sup +//sub u/ excimer emission in Na/sub 2/, predicted in 1980 by Konowalow and Julienne and observed recently by Dinev et al, was studied here in greater detail. Strong excimer emission (/similar to/30 nm) was observed for two-photon pumping to both sides of the unresolved 4D states, and weak excimer emission was seen when pumping near the 5D levels. The excimer emission exhibits a complicated pump laser profile with a pronounced ''dip'' at the 4d /sup 2/D two-photon resonance. Similarly, (2+1) photon ionization via the 3d /sup 2/D and 4d /sup 2/D states shows a dramatic decrease as the sodium density increases. These results can be attributed either to depleted 3d /sup 2/D or 4d /sup 2/D population due to stimulated electronic Raman scattering (SERS) or to the interference effects recently reported by Malcuit et al. and Krasnikov et al. and treated theoretically by Manykin and Afanas'ev and by Agarwal. It is argued thatmore » both mechanisms are operative.« less

•Dec 15, 1988•0 citations

Observation of four-wave mixing involving two quadrupole transitions in Na vapor

R. L. Panock, Richard R. Freeman, John E. Bjorkholm

We have observed a four-wave mixing process in sodium vapor in which two of the four waves are resonantly enhanced by electric quadrupole transitions. The atom is pumped via a quadrupole transition from the 3s to the 4d state with a single photon at 2894 Å. Intense coherent emission at 3427 Å corresponding to the 3d-3s transition can be observed exiting the Na cell only in the direction parallel to the input beam. Also observed coming from the cell is intense coherent light at 2.34 µm corresponding to the 4d-4s transition in Na.

Conference on Lasers and Electro-Optics•Jan 1, 1981•0 citations

Two-photon excitation of dense sodium vapor near the n d 2D5/2, 3/2 (n=3, 4, 5) levels: Na2 1 3Σ+g→1 3Σ+u excimer emission

Stanley J. Bajic, R. N. Compton, John A. D. Stockdale +1 more

Laser excitation and ionization processes in dense (1–10 Torr) sodium vapor have been studied for laser wavelengths near the two-photon allowed nd 2D(n=3, 4, 5) and ns 2S(n=4, 5, 6) states. In particular, the 1 3Σ+g→1 3Σ+u excimer emission in Na2, predicted in 1980 by Konowalow and Julienne and observed recently by Dinev et al, was studied here in greater detail. Strong excimer emission (∼830 nm) was observed for two-photon pumping to both sides of the unresolved 4D states, and weak excimer emission was seen when pumping near the 5D levels. The excimer emission exhibits a complicated pump laser profile with a pronounced ‘‘dip’’ at the 4d 2D two-photon resonance. Similarly, [2+1] photon ionization via the 3d 2D and 4d 2D states shows a dramatic decrease as the sodium density increases. These results can be attributed either to depleted 3d 2D or 4d 2D population due to stimulated electronic Raman scattering (SERS) or to the interference effects recently reported by Malcuit et al. and Krasnikov et al. and treated theoretically by Manykin and Afanas’ev and by Agarwal. It is argued that both mechanisms are operative. Strong ionization and SERS signals were observed at the hybrid resonances corresponding to 3p 2P3/2, 1/2 →4d 2D transitions; however, no excimer lasing at 830 nm was detected. No excimer emission was detected upon two-photon pumping near or at the 3d 2D or ns 2S(n=4, 5, 6) states. Based on these and other observations, the 1 3Σ+g→1 3Σ+u excimer emission is attributed to a molecular Raman process involving stimulated emission or six-wave mixing via a pathway of the type 1 3Σ+u→2hν 3Δu→ j 3Πg→(k 3Πu, l 3Σ +u)→1 3Σ+g→1 3Σ +u .

The Journal of Chemical Physics•Dec 15, 1988•12 citations

Saturation effects in multiphoton ionization

John A. Yeazell, Michelle S. Malcuit, Carlos R. Stroud +1 more

We have studied two-photon resonant three-photon ionization of atomic sodium vapor. A dye laser tuned to either the 4d or 5s two-photon allowed transition was used to excite the atom and a second more intense laser (λ = 7000 Å) was used for ionization. The ion yield was measured as a function of resonant laser intensity and detuning, the nonresonant laser intensity, and the temporal overlap of the exciting and ionizing laser pulses. We have found1 that at high laser intensities the photoionization yield decreases as the nonresonant laser intensity is increased. When tuned to the 5s level a value of ~−0.6 was obtained for the exponential index even with the resonant laser tuned to maximize the ion yield. A theoretical model including the effects of Stark shift of the ground state, power broadening of the intermediate level due to saturation of the two-photon transition and by rapid transitions to the ionization continuum was used to predict the experimental results. Good agreement between theory and experiment required the use of a photoionization cross section for the 5s level which was ~20 times greater than the accepted value. Results for photoionization from the 4d level are also presented.

Annual Meeting Optical Society of America•Jan 1, 1985•0 citations

Competition effect in atomic-molecular system

Jia Suo-Tang, Qin Lijuan, Qian Zu-liang +3 more

The competition effects among the processes of atomic ionization, optical pumped stimulated radiation (OPSR), four-wave frequency mixing (FWFM) and molecular stimulated diffuse band radiation at the atomic two-photon resonance of 3S approaches 4D in Na2 - Na mixture were observed. The dip at the two-photon resonance in the excitation spectrum for the diffuse-band radiation was interpreted as suppression of population in 4D state.

Acta Physica Sinica (Overseas Edition)•May 1, 1996•0 citations

Three-photon resonances due to autoionizing states in calcium

Anna M. Zawadzka, Roman S. Dygdała, Andrzej Raczyński +2 more

In the present study we have investigated three-photon ionization in Ca in which autoionizing states are engaged. The two-photon resonant process (from the Ca ground state 4s 2 1 S 0 ) occurred through or at least in the vicinity of one of the following states: 4s4d 1 D 2 , 4p 2 3 P 2 , 4s6s 1 S 0 , 4p 2 1 D 2 and 4p 2 1 S 0 , with the third photon either reaching the continuum directly or one of the autoionizing states. The three-photon resonant transitions to 3d m p, m f: 1 P 1 , 3 P 1 and 3 D 1 autoionizing states for m up to 21 have been observed. Some of the autoionizing resonances which we have found had not been observed before in a high-resolution one-photon absorption experiment (for J = 1) and in multiphoton experiments (for J = 3). We have compared the ionization signal as a function of the laser detuning and the laser intensity with theoretical curves obtained within a simple model (three-level atom + one-mode laser field). This gives information about the order of magnitude of the three-photon ionization probability through autoionizing states.

Journal of Physics B Atomic Molecular and Optical Physics•Apr 11, 2002•19 citations
Three-photon ionization of Na out of the 4d two-photon state is discussed. Results from an atomic beam and an atomic vapor in a heat pipe are compared. The 4d ionization in the vapor was a factor of 10/sup 4/ smaller than in the beam. Absorption in the vapor was less than concentration arguments might suggest. This reduction is explained by very fast processes which dump the resonant state into lower levels and by a process which suppresses the two-photon excitation at high concentrations. Experimental evidence of these processes was observed as strong infrared and ultraviolet emission in the forward direction corresponding to the 4d ..-->.. 4p and 4p ..-->.. 3s transition, respectively. 11 refs., 5 figs.
Laser excitation and ionization processes in dense (1--10 Torr) sodium vapor have been studied for laser wavelengths near the two-photon allowed nd /sup 2/D(n = 3, 4, 5) and ns /sup 2/S(n = 4, 5, 6) states. In particular, the 1 /sup 3//Sigma//sup +//sub g//yields/1 /sup 3//Sigma//sup +//sub u/ excimer emission in Na/sub 2/, predicted in 1980 by Konowalow and Julienne and observed recently by Dinev et al, was studied here in greater detail. Strong excimer emission (/similar to/30 nm) was observed for two-photon pumping to both sides of the unresolved 4D states, and weak excimer emission was seen when pumping near the 5D levels. The excimer emission exhibits a complicated pump laser profile with a pronounced ''dip'' at the 4d /sup 2/D two-photon resonance. Similarly, (2+1) photon ionization via the 3d /sup 2/D and 4d /sup 2/D states shows a dramatic decrease as the sodium density increases. These results can be attributed either to depleted 3d /sup 2/D or 4d /sup 2/D population due to stimulated electronic Raman scattering (SERS) or to the interference effects recently reported by Malcuit et al. and Krasnikov et al. and treated theoretically by Manykin and Afanas'ev and by Agarwal. It is argued thatmore » both mechanisms are operative.« less
We have observed a four-wave mixing process in sodium vapor in which two of the four waves are resonantly enhanced by electric quadrupole transitions. The atom is pumped via a quadrupole transition from the 3s to the 4d state with a single photon at 2894 Å. Intense coherent emission at 3427 Å corresponding to the 3d-3s transition can be observed exiting the Na cell only in the direction parallel to the input beam. Also observed coming from the cell is intense coherent light at 2.34 µm corresponding to the 4d-4s transition in Na.
Laser excitation and ionization processes in dense (1–10 Torr) sodium vapor have been studied for laser wavelengths near the two-photon allowed nd 2D(n=3, 4, 5) and ns 2S(n=4, 5, 6) states. In particular, the 1 3Σ+g→1 3Σ+u excimer emission in Na2, predicted in 1980 by Konowalow and Julienne and observed recently by Dinev et al, was studied here in greater detail. Strong excimer emission (∼830 nm) was observed for two-photon pumping to both sides of the unresolved 4D states, and weak excimer emission was seen when pumping near the 5D levels. The excimer emission exhibits a complicated pump laser profile with a pronounced ‘‘dip’’ at the 4d 2D two-photon resonance. Similarly, [2+1] photon ionization via the 3d 2D and 4d 2D states shows a dramatic decrease as the sodium density increases. These results can be attributed either to depleted 3d 2D or 4d 2D population due to stimulated electronic Raman scattering (SERS) or to the interference effects recently reported by Malcuit et al. and Krasnikov et al. and treated theoretically by Manykin and Afanas’ev and by Agarwal. It is argued that both mechanisms are operative. Strong ionization and SERS signals were observed at the hybrid resonances corresponding to 3p 2P3/2, 1/2 →4d 2D transitions; however, no excimer lasing at 830 nm was detected. No excimer emission was detected upon two-photon pumping near or at the 3d 2D or ns 2S(n=4, 5, 6) states. Based on these and other observations, the 1 3Σ+g→1 3Σ+u excimer emission is attributed to a molecular Raman process involving stimulated emission or six-wave mixing via a pathway of the type 1 3Σ+u→2hν 3Δu→ j 3Πg→(k 3Πu, l 3Σ +u)→1 3Σ+g→1 3Σ +u .
We have studied two-photon resonant three-photon ionization of atomic sodium vapor. A dye laser tuned to either the 4d or 5s two-photon allowed transition was used to excite the atom and a second more intense laser (λ = 7000 Å) was used for ionization. The ion yield was measured as a function of resonant laser intensity and detuning, the nonresonant laser intensity, and the temporal overlap of the exciting and ionizing laser pulses. We have found1 that at high laser intensities the photoionization yield decreases as the nonresonant laser intensity is increased. When tuned to the 5s level a value of ~−0.6 was obtained for the exponential index even with the resonant laser tuned to maximize the ion yield. A theoretical model including the effects of Stark shift of the ground state, power broadening of the intermediate level due to saturation of the two-photon transition and by rapid transitions to the ionization continuum was used to predict the experimental results. Good agreement between theory and experiment required the use of a photoionization cross section for the 5s level which was ~20 times greater than the accepted value. Results for photoionization from the 4d level are also presented.
In the present study we have investigated three-photon ionization in Ca in which autoionizing states are engaged. The two-photon resonant process (from the Ca ground state 4s 2 1 S 0 ) occurred through or at least in the vicinity of one of the following states: 4s4d 1 D 2 , 4p 2 3 P 2 , 4s6s 1 S 0 , 4p 2 1 D 2 and 4p 2 1 S 0 , with the third photon either reaching the continuum directly or one of the autoionizing states. The three-photon resonant transitions to 3d m p, m f: 1 P 1 , 3 P 1 and 3 D 1 autoionizing states for m up to 21 have been observed. Some of the autoionizing resonances which we have found had not been observed before in a high-resolution one-photon absorption experiment (for J = 1) and in multiphoton experiments (for J = 3). We have compared the ionization signal as a function of the laser detuning and the laser intensity with theoretical curves obtained within a simple model (three-level atom + one-mode laser field). This gives information about the order of magnitude of the three-photon ionization probability through autoionizing states.