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Study of collisional redistribution using two-photon absorption with a nearly resonant intermediate state

P. R. Berman, P. F. Liao, John E. Bjorkholm

Published Sep 1, 1979• 0 citations
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Abstract

We report studies of collision-induced features of the 3S(1/2) yields 3P(1/2) yields 4D(3/2) two-photon absorption in atomic sodium vapor undergoing collisionss with several rare gas perturbers. The results yield the collisional redistribution function which describes the nonresonant excitation of the 3P(1/2) intermediate state. Good agreement with theory is obtained only if effects of 3P(1/2) in equilibrium with 3P(3/2) state-changing collisions are included in the calculations. Results are used to obtain a value for a pressure broadening coefficient in the Na-Kr system. (Author)

Related papers

Study of collisional redistribution using two-photon absorption with a nearly-resonant intermediate state

P. F. Liao, John E. Bjorkholm, P. R. Berman

The authors report studies of collision-induced features of the $3{S}_{\frac{1}{2}}\ensuremath{\rightarrow}3{P}_{\frac{1}{2}}\ensuremath{\rightarrow}4{D}_{\frac{3}{2}}$ two-photon absorption in atomic-sodium vapor undergoing collisions with several rare-gas perturbers. The results yield the collisional redistribution function which describes the nonresonant excitation of the $3{P}_{\frac{1}{2}}$ intermediate state. Good agreement with theory is obtained only if effects of $3{P}_{\frac{1}{2}}\ensuremath{\leftrightarrow}3{P}_{\frac{3}{2}}$ state-changing collisions are included in the calculations. Results are used to obtain a value for a pressure-broadening coefficient in the Na-Kr system.

Physical Review A•Oct 1, 1979•35 citations

Effects of velocity-changing collisions on two-photon and stepwise-absorption spectroscopic line shapes

P. F. Liao, John E. Bjorkholm, P. R. Berman

We report the results of an experimental study of the effects of velocity-changing collisions on two-photon and stepwise-absorption line shapes. Excitation spectra for the $3{S}_{\frac{1}{2}}\ensuremath{\rightarrow}3{P}_{\frac{1}{2}}\ensuremath{\rightarrow}4{D}_{\frac{1}{2}}$ transitions of sodium atoms undergoing collisions with foreign gas perturbers are obtained. These spectra are obtained with two cw dye lasers. One laser, the pump laser, is tuned 1.6 GHz below the $3{S}_{\frac{1}{2}}\ensuremath{\rightarrow}3{P}_{\frac{1}{2}}$ transition frequency and excites a nonthermal longitudinal velocity distribution of excited $3{P}_{\frac{1}{2}}$ atoms in the vapor. Absorption of the second (probe) laser is used to monitor the steady-state excited-state distribution which is a result of collisions with rare gas atoms. The spectra are obtained for various pressures of He, Ne, and Kr gases and are fit to a theoretical model which utilizes either the phenomenological Keilson-St\"orer or the classical hardsphere collision kernel. The theoretical model includes the effects of collisionally aided excitation of the $3{P}_{\frac{1}{2}}$ state as well as effects due to fine-structure state-changing collisions. Although both kernels are found to predict line shapes which are in reasonable agreement with the experimental results, the hard-sphere kernel is found superior as it gives a better description of the effects of large-angle scattering for heavy perturbers. Neither kernel provides a fully adequate description over the entire line profile. The experimental data is used to extract effective hard-sphere collision cross sections for collisions between sodium $3{P}_{\frac{1}{2}}$ atoms and helium, neon, and krypton perturbers.

Physical Review A•Jun 1, 1980•74 citations

Collisional modification of the atomic-Na 3s 2 S1/2 –5s 2 S1/2 two-color two-photon polarization spectrum

LeRoy F. Cook, D. A. Olsgaard, Mark D. Havey +1 more

An experimental investigation of the atomic-Na 3s $^{2}$${\mathit{S}}_{1/2--}$5s $^{2}$${\mathit{S}}_{1/2}$ two-color two-photon polarization spectrum has been made. Measurements of the linear polarization degree of the two-photon transition were made for one laser tuned within a \ifmmode\pm\else\textpm\fi{}100 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ range of the atomic-Na 3p $^{2}$${\mathit{P}}_{\mathit{j}}$ levels, with the second adjusted to satisfy the two-photon resonance condition. The relatively short-pulse (\ensuremath{\sim}0.5 ns) lasers used eliminate effects on the spectrum due to atomic-Na hyperfine interactions and radiation trapping, while greatly reducing depolarization due to collisions with Ar gas. In the absence of collisions, the measured polarization spectrum is in excellent agreement with calculations. Measurements of the Ar pressure dependence of the spectrum revealed strong depolarization in the vicinity of resonant excitation through the 3p $^{2}$${\mathit{P}}_{3/2}$ level. A collisional depolarization cross section of 200(30) \AA{} for this process was deduced from the data.

Physical Review A•Jan 1, 1993•16 citations

Calculated pressure broadening and shift for the sodium atom perturbed by rare gases. II. Two-photon 3S−nS transitions ( n=6−9 )

Chao Wu, William C. Stwalley

Our recent treatment [Phys. Rev. A 18, 1066 (1978)] of the broadening and shift of alkali-metal-atom two-photon $S\ensuremath{-}S$ transitions is applied to the Na $3S\ensuremath{-}\mathrm{nS}$ transitions ($n=6\ensuremath{-}9$) perturbed by Ar, Kr, and Xe rare gases. Comparison with recent experimental data [A. Flusberg et al., Phys. Rev. A 19, 1607 (1979)] on the Na-Ar pair for $n\ensuremath{\le}7$ shows good agreement. However, for transitions to $n>8$ the calculated pressure effects no longer agree well with experimental data; presumably the pressure effects cannot be adequately described by a simple two-body long-range impact theory.

Physical Review A•Aug 1, 1981•7 citations

Collisional processes in sodium vapour optically excited to the 3P state: asymptotic calculations

Pawel Kowalczyk

Studies two mechanisms for the non-resonant population of the sodium 4D state when sodium vapour is optically excited to the 3P state. They are the energy-pooling collision of two 3P-excited atoms and the radiative collision involving a laser photon. Both processes are considered in the region of large interatomic distances. Results are compared with experimental data.

Journal of Physics B Atomic and Molecular Physics•Mar 14, 1984•23 citations

Collision-Induced Two-Photon Absorption of Ultrashort Light Pulses

Kenji Torizuka, Norio Morita, Tatsuo Yajima

The relation between the spectral character of a completely off-resonant two-photon absorption and the non-impact collision dynamics of a three-level atomic system is studied. A collisionally induced resonance character in the spectral dependence of the absorption probability is shown theoretically. Measured results about the dependence of fluorescence intensity on the incident light frequencies are ingood agreement with the theory. The interatomic potential between the sodium 4D state and argon is also estimated from experimental results.

Journal of the Physical Society of Japan•Jul 15, 1987•1 citation
We report studies of collision-induced features of the 3S(1/2) yields 3P(1/2) yields 4D(3/2) two-photon absorption in atomic sodium vapor undergoing collisionss with several rare gas perturbers. The results yield the collisional redistribution function which describes the nonresonant excitation of the 3P(1/2) intermediate state. Good agreement with theory is obtained only if effects of 3P(1/2) in equilibrium with 3P(3/2) state-changing collisions are included in the calculations. Results are used to obtain a value for a pressure broadening coefficient in the Na-Kr system. (Author)
The authors report studies of collision-induced features of the $3{S}_{\frac{1}{2}}\ensuremath{\rightarrow}3{P}_{\frac{1}{2}}\ensuremath{\rightarrow}4{D}_{\frac{3}{2}}$ two-photon absorption in atomic-sodium vapor undergoing collisions with several rare-gas perturbers. The results yield the collisional redistribution function which describes the nonresonant excitation of the 3P123{P}_{\frac{1}{2}}3P21​​ intermediate state. Good agreement with theory is obtained only if effects of $3{P}_{\frac{1}{2}}\ensuremath{\leftrightarrow}3{P}_{\frac{3}{2}}$ state-changing collisions are included in the calculations. Results are used to obtain a value for a pressure-broadening coefficient in the Na-Kr system.
We report the results of an experimental study of the effects of velocity-changing collisions on two-photon and stepwise-absorption line shapes. Excitation spectra for the $3{S}_{\frac{1}{2}}\ensuremath{\rightarrow}3{P}_{\frac{1}{2}}\ensuremath{\rightarrow}4{D}_{\frac{1}{2}}$ transitions of sodium atoms undergoing collisions with foreign gas perturbers are obtained. These spectra are obtained with two cw dye lasers. One laser, the pump laser, is tuned 1.6 GHz below the $3{S}_{\frac{1}{2}}\ensuremath{\rightarrow}3{P}_{\frac{1}{2}}$ transition frequency and excites a nonthermal longitudinal velocity distribution of excited 3P123{P}_{\frac{1}{2}}3P21​​ atoms in the vapor. Absorption of the second (probe) laser is used to monitor the steady-state excited-state distribution which is a result of collisions with rare gas atoms. The spectra are obtained for various pressures of He, Ne, and Kr gases and are fit to a theoretical model which utilizes either the phenomenological Keilson-St\"orer or the classical hardsphere collision kernel. The theoretical model includes the effects of collisionally aided excitation of the 3P123{P}_{\frac{1}{2}}3P21​​ state as well as effects due to fine-structure state-changing collisions. Although both kernels are found to predict line shapes which are in reasonable agreement with the experimental results, the hard-sphere kernel is found superior as it gives a better description of the effects of large-angle scattering for heavy perturbers. Neither kernel provides a fully adequate description over the entire line profile. The experimental data is used to extract effective hard-sphere collision cross sections for collisions between sodium 3P123{P}_{\frac{1}{2}}3P21​​ atoms and helium, neon, and krypton perturbers.
An experimental investigation of the atomic-Na 3s 2^{2}2${\mathit{S}}_{1/2--}$5s 2^{2}2S1/2{\mathit{S}}_{1/2}S1/2​ two-color two-photon polarization spectrum has been made. Measurements of the linear polarization degree of the two-photon transition were made for one laser tuned within a \ifmmode\pm\else\textpm\fi{}100 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ range of the atomic-Na 3p 2^{2}2Pj{\mathit{P}}_{\mathit{j}}Pj​ levels, with the second adjusted to satisfy the two-photon resonance condition. The relatively short-pulse (\ensuremath{\sim}0.5 ns) lasers used eliminate effects on the spectrum due to atomic-Na hyperfine interactions and radiation trapping, while greatly reducing depolarization due to collisions with Ar gas. In the absence of collisions, the measured polarization spectrum is in excellent agreement with calculations. Measurements of the Ar pressure dependence of the spectrum revealed strong depolarization in the vicinity of resonant excitation through the 3p 2^{2}2P3/2{\mathit{P}}_{3/2}P3/2​ level. A collisional depolarization cross section of 200(30) \AA{} for this process was deduced from the data.
Our recent treatment [Phys. Rev. A 18, 1066 (1978)] of the broadening and shift of alkali-metal-atom two-photon $S\ensuremath{-}S$ transitions is applied to the Na $3S\ensuremath{-}\mathrm{nS}$ transitions ($n=6\ensuremath{-}9$) perturbed by Ar, Kr, and Xe rare gases. Comparison with recent experimental data [A. Flusberg et al., Phys. Rev. A 19, 1607 (1979)] on the Na-Ar pair for $n\ensuremath{\le}7$ shows good agreement. However, for transitions to n>8n>8n>8 the calculated pressure effects no longer agree well with experimental data; presumably the pressure effects cannot be adequately described by a simple two-body long-range impact theory.
The relation between the spectral character of a completely off-resonant two-photon absorption and the non-impact collision dynamics of a three-level atomic system is studied. A collisionally induced resonance character in the spectral dependence of the absorption probability is shown theoretically. Measured results about the dependence of fluorescence intensity on the incident light frequencies are ingood agreement with the theory. The interatomic potential between the sodium 4D state and argon is also estimated from experimental results.