The Journal of Chemical Physics

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

J. Weiner, Penelope Polak-Dingels

Published Jan 1, 1981• 40 citations

Abstract

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.

DOI: 10.1063/1.440858

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The Journal of Chemical Physics

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

J. Weiner, Penelope Polak-Dingels

Published Jan 1, 1981• 40 citations

Publisher

Abstract

DOI: 10.1063/1.440858

Related papers

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Physical Review AJan 1, 199511 citations

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.

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.