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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, Daniel D. Konowalow

Published Dec 15, 1988• 0 citations
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Abstract

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

Related papers

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

RIS and competing processes in high concentration atomic vapors

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

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.

•Aug 1, 1986•3 citations

Stimulated excited-state Raman scattering and three-photon scattering in sodium

Yaakov Shevy, Harry Friedmann, M. Rosenbluh

We have observed stimulated emission from Na vapor excited by a laser tuned near the Na D lines. The stimulated-emission processes have been identified as Rayleigh scattering, excited-state Raman scattering, and ordinary as well as resonance-enhanced three-photon scattering. The observations indicate that at least part of the conical emission observed in many systems has its origin in these processes.

Optics Letters•Feb 1, 1986•12 citations

Observation of stimulated emission of Na2 at 0.75-0.80 µm by UV excitation

Yuezhen Sun, Zhongxian Chen, Miao Du

We describe the first observation of stimulated emission at 0.75–0.80 µm and at 1.06–1.14 µm in sodium vapor at 580°C and 0.5-Torr buffer argon pressure by single-UV-photon or two-visible-photon pumping. For our pumping source, we used a XeCl excimer laser (EMG 101)–dye laser (FL2002), wavelengths 3375.93-Å (PTP) and 5772.8- Å (Rh6G) for single-photon and two-photon excitation with 0.16- Å linewidth and 10-nm pulse width; heating zone of the heat-pipe 25 cm.

Annual Meeting Optical Society of America•Jan 1, 1986•0 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

STIMULATED EMISSION BASED ON TWO-STEP HYBRID RESONANCE $A^{1}\Sigma_{u}^{+}$ OR $B^{1}\Pi_{u}$ STATE OF $Na.^{*}$

L. J. Qin, Z. G. Wang, K. C. Zhang +1 more

The first step of the hybrid excitation in the experiment was achieved by using a pulse broadband ($\\sim$200 {\\AA}) dye laser beam through a heat pipe oven. But the total covered pumping wavelength region from 4600 {\\AA} to 6800 {\\AA} the populated upper electronic state in $Na_{2}$ should be either $A^{\\prime}\\Sigma_{u}$ or $B^{\\prime}\\Pi_{u}$ state. The excited sodium dimers $Na_{2}^{\\ast}$ transfered their energy to sodium atoms Na by near resonace collisions and the Na then would populate up the 3P level from ground state 3s. The Na were consequentely pumped up to 4D, 5D, 5S or 6S level from 3P by using a narrowband dye laser pumped by the same $N_{2}$ laser. The infrared stimulated radiation corresponding to the transitions of 4D-4P(2.34 $\\mu$m). 5D-4P(5.02$\\mu$m), 5S-4P(3.42 $\\mu$m) and 6S-5P(7.52 $\\mu$m) with cascade stimulated emission from 4P to 4S (2.20 $\\mu$m) and from 5P to 5S (5.43 $\\mu$m) were then obtained, Furthermore the dependence of the output energy on the pumping wavelengthes was measured and discussed.

•Jan 1, 1985•0 citations
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
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 .
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.
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.
STIMULATED EMISSION BASED ON TWO-STEP HYBRID RESONANCE A1Σu+A^{1}\Sigma_{u}^{+}A1Σu+​ OR B1ΠuB^{1}\Pi_{u}B1Πu​ STATE OF Na.∗Na.^{*}Na.∗
The first step of the hybrid excitation in the experiment was achieved by using a pulse broadband ($\\sim$200 {\\AA}) dye laser beam through a heat pipe oven. But the total covered pumping wavelength region from 4600 {\\AA} to 6800 {\\AA} the populated upper electronic state in Na2Na_{2}Na2​ should be either AprimeSigmauA^{\\prime}\\Sigma_{u}AprimeSigmau​ or BprimePiuB^{\\prime}\\Pi_{u}BprimePiu​ state. The excited sodium dimers Na2astNa_{2}^{\\ast}Na2ast​ transfered their energy to sodium atoms Na by near resonace collisions and the Na then would populate up the 3P level from ground state 3s. The Na were consequentely pumped up to 4D, 5D, 5S or 6S level from 3P by using a narrowband dye laser pumped by the same N2N_{2}N2​ laser. The infrared stimulated radiation corresponding to the transitions of 4D-4P(2.34 mu\\mumum). 5D-4P(5.02mu\\mumum), 5S-4P(3.42 mu\\mumum) and 6S-5P(7.52 mu\\mumum) with cascade stimulated emission from 4P to 4S (2.20 mu\\mumum) and from 5P to 5S (5.43 mu\\mumum) were then obtained, Furthermore the dependence of the output energy on the pumping wavelengthes was measured and discussed.