Journal of Physics B Atomic and Molecular Physics

Associative ionisation of laser excited sodium in an atomic beam

A de Jong, F. van der Valk

Published Sep 28, 1979• 56 citations

Abstract

The authors have observed ion formation when a non-velocity-selected atomic sodium beam is irradiated with a CW dye laser tuned to one of the D-lines. The ions are formed by associative ionisation according to Na(3P)+Na(3P) to Na 2 + +e, with an effective cross section of about 5*10 -18 cm 2 at a mean relative kinetic energy of 0.007 eV.

DOI: 10.1088/0022-3700/12/18/006

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Journal of Physics B Atomic and Molecular Physics

Associative ionisation of laser excited sodium in an atomic beam

A de Jong, F. van der Valk

Published Sep 28, 1979• 56 citations

Publisher

Abstract

DOI: 10.1088/0022-3700/12/18/006

Related papers

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Charles Tapalian, W. W. Smith

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The formation of ${\mathrm{Na}}^{+}$ and ${\mathrm{Na}}_{2}^{+}$ in laser-irradiated sodium vapor has been studied using a nitrogen-laser-pumped dye laser. The effects of irradiation by this pulsed laser are substantially different from those reported previously using a cw device, but otherwise identical experimental conditions. In contrast to the earlier experiments, in which ions were observed only when the cw laser was tuned to a $D$ line, relatively large "background" ion signals are observed at all excitation wavelengths, a result of multiphoton processes involving the ${\mathrm{Na}}_{2}$ component of the vapor. It is shown that the laser bandwidth and pulse duration are extremely important parameters; a wide bandwidth effectively magnifying the importance of the dimer component of the vapor and a short pulse duration minimizing the effects of interactions between excited atoms and molecules.The formation of ${\mathrm{Na}}^{+}$ and ${\mathrm{Na}}_{2}^{+}$ in laser-irradiated sodium vapor has been studied using a nitrogen-laser-pumped dye laser. The effects of irradiation by this pulsed laser are substantially different from those reported previously using a cw device, but otherwise identical experimental conditions. In contrast to the earlier experiments, in which ions were observed only when the cw laser was tuned to a $D$ line, relatively large "background" ion signals are observed at all excitation wavelengths, a result of multiphoton processes involving the ${\mathrm{Na}}_{2}$ component of the vapor. It is shown that the laser bandwidth and pulse duration are extremely important parameters; a wide bandwidth effectively magnifying the importance of the dimer component of the vapor and a short pulse duration minimizing the effects of interactions between excited atoms and molecules.

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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.

Journal of Physics B Atomic Molecular and Optical PhysicsJun 28, 19972 citations

We have observed ion formation (both

{\mathrm{Na}}^{+}

and

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

) and radiation from high-lying Na states when low-density vapor (\ensuremath{\sim}

{10}^{13}

${\mathrm{cm}}^{\ensuremath{-}3}$) is irradiated with a cw dye laser tuned to one of the

D

lines. The

{\mathrm{Na}}^{+}

ions probably result from photodissociation of

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

formed by $\mathrm{Na}(3p)\ensuremath{-}\mathrm{Na}(3p)$ associative ionization, while the high-lying radiating states are formed in energy-pooling reactions.

The formation of

{\mathrm{Na}}^{+}

and

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

in laser-irradiated sodium vapor has been studied using a nitrogen-laser-pumped dye laser. The effects of irradiation by this pulsed laser are substantially different from those reported previously using a cw device, but otherwise identical experimental conditions. In contrast to the earlier experiments, in which ions were observed only when the cw laser was tuned to a

D

line, relatively large "background" ion signals are observed at all excitation wavelengths, a result of multiphoton processes involving the

{\mathrm{Na}}_{2}

component of the vapor. It is shown that the laser bandwidth and pulse duration are extremely important parameters; a wide bandwidth effectively magnifying the importance of the dimer component of the vapor and a short pulse duration minimizing the effects of interactions between excited atoms and molecules.