Physical Review Letters

Observation of Structure in Laser-Induced Penning and Associative Ionization in Crossed-Beam Na + Na Collisions

Penelope Polak-Dingels, J. F. Delpech, J. Weiner

Published Jun 23, 1980• 64 citations

Abstract

The results of double-laser experiments in which ${\mathrm{Na}}_{2}^{+}$ and ${\mathrm{Na}}^{+}$ are produced in crossed alkali beams under single-collision conditions in the presence of strong optical fields are reported. Structure in the mass-selected product ion intensity as a function laser frequency is observed when the optical field is strongly focused and tuned far off atomic or dimer transitions. These measurements are the first to show that the nuclear motion of the quasimolecular collision intermediate plays an important role in laser-induced collisional ionization.

DOI: 10.1103/physrevlett.44.1663

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Penning and associative ionization in crossed-beam Na/Na collisions assisted by strong resonant laser fields

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Physical Review Letters

Observation of Structure in Laser-Induced Penning and Associative Ionization in Crossed-Beam Na + Na Collisions

Penelope Polak-Dingels, J. F. Delpech, J. Weiner

Published Jun 23, 1980• 64 citations

Publisher

Abstract

The results of double-laser experiments in which

{\mathrm{Na}}_{2}^{+}

and

{\mathrm{Na}}^{+}

are produced in crossed alkali beams under single-collision conditions in the presence of strong optical fields are reported. Structure in the mass-selected product ion intensity as a function laser frequency is observed when the optical field is strongly focused and tuned far off atomic or dimer transitions. These measurements are the first to show that the nuclear motion of the quasimolecular collision intermediate plays an important role in laser-induced collisional ionization.

DOI: 10.1103/physrevlett.44.1663

Related papers

Penning and associative ionization in crossed-beam Na/Na collisions assisted by strong resonant laser fields

J. Weiner, Penelope Polak-Dingels

We observe the production of Na2+ and Na+ arising from single collisions between crossed beams of sodium atoms when a laser field is tuned near the Na(3p 2P3/2) and Na(3p 2P1/2) transitions. Measurements of ion intensity vs laser intensity show that at moderately high power true laser-induced processes dominate over purely collisional effects. Relative intensity of mass-selected ions produced at either member of the Na resonance doublet shows conclusively that Na+ does not arise simply from photodissociation of Na2+ but must result from a direct, laser-induced collisional ionization.We observe the production of Na2+ and Na+ arising from single collisions between crossed beams of sodium atoms when a laser field is tuned near the Na(3p 2P3/2) and Na(3p 2P1/2) transitions. Measurements of ion intensity vs laser intensity show that at moderately high power true laser-induced processes dominate over purely collisional effects. Relative intensity of mass-selected ions produced at either member of the Na resonance doublet shows conclusively that Na+ does not arise simply from photodissociation of Na2+ but must result from a direct, laser-induced collisional ionization.

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Efficient collisional dissociation of Na{sub 2}{sup +} by laser-excited Na (3p)

Charles Tapalian, W. W. Smith

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Bulletin of the American Physical SocietyMay 1, 19930 citations

Observation of Laser-Induced Penning and Associative Ionization in Li-Li Collisions

A. v. Hellfeld, J. Caddick, J. Weiner

We report the direct observation of $^{6}\mathrm{Li}^{+}$ , $^{7}\mathrm{Li}^{+}$ , $^{13}\mathrm{Li}_{2}^{+}$ , $^{14}\mathrm{Li}_{2}^{+}$ arising from single collisions between beams of lithium atoms in the presence of a laser field. Although the relative intensity of atomic ions reflects the natural isotopic abundance, a pronounced enrichment of $^{13}\mathrm{Li}_{2}^{+}$ relative to $^{14}\mathrm{Li}_{2}^{+}$ is observed.We report the direct observation of $^{6}\mathrm{Li}^{+}$, $^{7}\mathrm{Li}^{+}$, $^{13}\mathrm{Li}_{2}^{+}$, $^{14}\mathrm{Li}_{2}^{+}$ arising from single collisions between beams of lithium atoms in the presence of a laser field. Although the relative intensity of atomic ions reflects the natural isotopic abundance, a pronounced enrichment of $^{13}\mathrm{Li}_{2}^{+}$ relative to $^{14}\mathrm{Li}_{2}^{+}$ is observed.

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Associative ionization in collisions between excited Na atoms in the and the states

Jan Jette Blange, G Aben, H. Rudolph +2 more

For the first time, associative ionization has been observed in an atomic beam of excited sodium atoms in both the and the state. Relative values for the partial cross sections were obtained specified according to the different magnetic substate combinations of the two fine-structure states. These were found to be comparable to those for associative ionization between two atoms. However, the effect of the excitation on the ion production rate was found to be considerable and to depend strongly on the relative polarizations of the laser beams producing the two populations due to the redistribution of the involved magnetic sublevels. The results indicate that the initial orientation of the electron spin S does not significantly influence the associative ionization reaction at the mean collision energy of 25 meV.For the first time, associative ionization has been observed in an atomic beam of excited sodium atoms in both the and the state. Relative values for the partial cross sections were obtained specified according to the different magnetic substate combinations of the two fine-structure states. These were found to be comparable to those for associative ionization between two atoms. However, the effect of the excitation on the ion production rate was found to be considerable and to depend strongly on the relative polarizations of the laser beams producing the two populations due to the redistribution of the involved magnetic sublevels. The results indicate that the initial orientation of the electron spin S does not significantly influence the associative ionization reaction at the mean collision energy of 25 meV.

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Ultracold photoassociative ionization collisions in an atomic beam: Optical field intensity and polarization dependence of the rate constant

Chun-Cheng Tsao, Reginaldo de Jesus Napolitano, Yang Wang +1 more

We report here measurements of two-body photoassociative ionization collisions between sodium atoms within an ultranarrow velocity class selected from a well-collimated, thermal atomic beam. Doppler-shifted excitation of the Na(3s ${\mathrm{}}^{2}$ ${\mathit{S}}_{1/2}$ ;F=1)\ensuremath{\rightarrow}Na(5p ${\mathrm{}}^{2}$ ${\mathit{P}}_{3/2}$ ) transition at 285 nm by a single-mode laser defines the narrow velocity class that subsequently populates the F=2 hyperfine level of the Na ground state by optical pumping. Probe laser beam excitation tuned near the Na(3s ${\mathrm{}}^{2}$ ${\mathit{S}}_{1/2}$ ;F=2)\ensuremath{\rightarrow}Na(3p ${\mathrm{}}^{2}$ ${\mathit{P}}_{3/2}$ ;F=3) transition produced photoassociative ionization with an average collision energy ${\mathit{E}}_{\mathit{K}}$ corresponding to a temperature of 5.3 mK ( ${\mathit{E}}_{\mathit{K}}$ =3/2kT). We determine the rate constant for the process as a function of probe beam intensity and polarization.We report here measurements of two-body photoassociative ionization collisions between sodium atoms within an ultranarrow velocity class selected from a well-collimated, thermal atomic beam. Doppler-shifted excitation of the Na(3s${\mathrm{}}^{2}$${\mathit{S}}_{1/2}$;F=1)\ensuremath{\rightarrow}Na(5p${\mathrm{}}^{2}$${\mathit{P}}_{3/2}$) transition at 285 nm by a single-mode laser defines the narrow velocity class that subsequently populates the F=2 hyperfine level of the Na ground state by optical pumping. Probe laser beam excitation tuned near the Na(3s${\mathrm{}}^{2}$${\mathit{S}}_{1/2}$;F=2)\ensuremath{\rightarrow}Na(3p${\mathrm{}}^{2}$${\mathit{P}}_{3/2}$;F=3) transition produced photoassociative ionization with an average collision energy ${\mathit{E}}_{\mathit{K}}$ corresponding to a temperature of 5.3 mK (${\mathit{E}}_{\mathit{K}}$=3/2kT). We determine the rate constant for the process as a function of probe beam intensity and polarization.

Physical Review AJan 1, 199511 citations

Collisional and thermal ionization of sodium Rydberg atoms in single and crossed atomic beams

I. I. Ryabtsev, Ilya I. Beterov, Denis B. Tretyakov +4 more

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEMar 1, 20060 citations

The results of double-laser experiments in which

{\mathrm{Na}}_{2}^{+}

and

{\mathrm{Na}}^{+}

We report the direct observation of

^{6}\mathrm{Li}^{+}

^{7}\mathrm{Li}^{+}

^{13}\mathrm{Li}_{2}^{+}

^{14}\mathrm{Li}_{2}^{+}

arising from single collisions between beams of lithium atoms in the presence of a laser field. Although the relative intensity of atomic ions reflects the natural isotopic abundance, a pronounced enrichment of

^{13}\mathrm{Li}_{2}^{+}

relative to

^{14}\mathrm{Li}_{2}^{+}

is observed.

{\mathrm{}}^{2}

{\mathit{S}}_{1/2}

;F=1)\ensuremath{\rightarrow}Na(5p

{\mathrm{}}^{2}

{\mathit{P}}_{3/2}

) transition at 285 nm by a single-mode laser defines the narrow velocity class that subsequently populates the F=2 hyperfine level of the Na ground state by optical pumping. Probe laser beam excitation tuned near the Na(3s

{\mathrm{}}^{2}

{\mathit{S}}_{1/2}

;F=2)\ensuremath{\rightarrow}Na(3p

{\mathrm{}}^{2}

{\mathit{P}}_{3/2}

;F=3) transition produced photoassociative ionization with an average collision energy

{\mathit{E}}_{\mathit{K}}

corresponding to a temperature of 5.3 mK (

{\mathit{E}}_{\mathit{K}}

=3/2kT). We determine the rate constant for the process as a function of probe beam intensity and polarization.