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Physics of Electronic and Atomic Collisions: ICPEAC X

Cross sections for production of atomic magnetic sublevels in collisions between alkali ions and mercury atoms

Vincenz̊o Aquilanti, Piergiorgio Casavecchia, G. Grossi

Published Jan 1, 1977• 0 citations
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Asymmetry of cross sections for transitions between magnetic sublevels in atomic collisions

E. I. Dashevskaya, E. E. Nikitin, Stanislav Ya Umanskii

OptSp•Dec 1, 1983•1 citation

Measurement of Spin-Exchange Cross Sections for Cs133 , Rb87 , Rb85 , K39 , and Na23

N Ressler, Richard H. Sands, Thomas Edison. Stark

This paper reports measurements to determine the spin-exchange cross section for collisions between like alkali atoms. The spin-exchange cross section is determined for ${\mathrm{Cs}}^{133}$, ${\mathrm{Rb}}^{87}$, ${\mathrm{Rb}}^{85}$, ${\mathrm{K}}^{39}$, and ${\mathrm{Na}}^{23}$. The lifetime of the alkali atoms in the Zeeman sublevels of the ground-state hyperfine levels is dominated by spin-exchange collisions. The spin-exchange collision rate is therefore reflected by the linewidth of the microwave absorption spectrum observed in the magnetic dipole transitions between various of the Zeeman sublevels. The measurements employed an $X$-band electron paramagnetic resonance spectrometer. The alkali metal was distilled into a sample bulb which was placed inside a Dewar in a resonant cavity. The bulb was then heated to a temperature corresponding to an equilibrium vapor density of approximately ${10}^{15}$ alkali atoms/c.c. and the microwave absorption spectrum was recorded. In order to relate the spin-exchange rate to a cross section, it is necessary to determine the alkali density. This was done by comparing the intensity of the alkali EPR absorption to that of a weighed and oriented copper sulfate crystal. For ${\mathrm{Cs}}^{133}$ and ${\mathrm{Rb}}^{87}$, interpretation of the linewidth data is complicated by the fact that the transitions occur in a region where there is appreciable mixing of the high-field spin states by the hyperfine interaction. A density-matrix description of spin exchange which corrects for this intermediate field mixing is discussed, and the corrections are applied to the measured cross sections for two transitions in ${\mathrm{Cs}}^{133}$ and ${\mathrm{Rb}}^{87}$. Relative cross sections, referred to that of ${\mathrm{Na}}^{23}$, are also given.

Physical Review•Aug 5, 1969•69 citations

Probabilities of transitions between degenerated atomic magnetic sublevels induced by collisions

A. G. Petrashen, V. N. Rebane, T. K. Rebane

•Jan 1, 1973•0 citations

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.

Journal of Physics B Atomic Molecular and Optical Physics•Jun 28, 1997•2 citations

Atomic Collisions with Transitions Between Zeeman Sublevels

Ju. A. Vdovin, Valery M. Yermachenko, V. K. Maskevitsh

Physics of Electronic and Atomic Collisions: ICPEAC VII•Jan 1, 1971•0 citations

J mixing in nD (n=10-14) states of caesium induced in collisions with noble-gas atoms

M. Łukaszewski, I. Jackowska

Cross sections for the J mixing (transfer of excitation between fine-structure sublevels) in the nD (n=10-14) states of caesium due to collisions with noble-gas atoms are measured by the integrated intensities method. It is found that the cross sections corresponding to the different noble-gas perturbers are of the same order of magnitude for lower values of the principal quantum number n but become increasingly different from each other with increasing n and for n=13 and 14 the difference approaches two orders of magnitude. Qualitatively, the n-dependence of the cross sections is similar to that obtained in the studies of the l-mixing collisions in the Rydberg states of the alkali-metal atoms. The results are compared with those predicted by the existing theoretical models. Good agreement is obtained for He and Ne perturbers with the results of calculations by Sirko et al. in which the Fermi pseudopotential and perturbation approach were employed.

Journal of Physics B Atomic Molecular and Optical Physics•Apr 28, 1991•9 citations
This paper reports measurements to determine the spin-exchange cross section for collisions between like alkali atoms. The spin-exchange cross section is determined for Cs133{\mathrm{Cs}}^{133}Cs133, Rb87{\mathrm{Rb}}^{87}Rb87, Rb85{\mathrm{Rb}}^{85}Rb85, K39{\mathrm{K}}^{39}K39, and Na23{\mathrm{Na}}^{23}Na23. The lifetime of the alkali atoms in the Zeeman sublevels of the ground-state hyperfine levels is dominated by spin-exchange collisions. The spin-exchange collision rate is therefore reflected by the linewidth of the microwave absorption spectrum observed in the magnetic dipole transitions between various of the Zeeman sublevels. The measurements employed an XXX-band electron paramagnetic resonance spectrometer. The alkali metal was distilled into a sample bulb which was placed inside a Dewar in a resonant cavity. The bulb was then heated to a temperature corresponding to an equilibrium vapor density of approximately 1015{10}^{15}1015 alkali atoms/c.c. and the microwave absorption spectrum was recorded. In order to relate the spin-exchange rate to a cross section, it is necessary to determine the alkali density. This was done by comparing the intensity of the alkali EPR absorption to that of a weighed and oriented copper sulfate crystal. For Cs133{\mathrm{Cs}}^{133}Cs133 and Rb87{\mathrm{Rb}}^{87}Rb87, interpretation of the linewidth data is complicated by the fact that the transitions occur in a region where there is appreciable mixing of the high-field spin states by the hyperfine interaction. A density-matrix description of spin exchange which corrects for this intermediate field mixing is discussed, and the corrections are applied to the measured cross sections for two transitions in Cs133{\mathrm{Cs}}^{133}Cs133 and Rb87{\mathrm{Rb}}^{87}Rb87. Relative cross sections, referred to that of Na23{\mathrm{Na}}^{23}Na23, are also given.
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.
Cross sections for the J mixing (transfer of excitation between fine-structure sublevels) in the nD (n=10-14) states of caesium due to collisions with noble-gas atoms are measured by the integrated intensities method. It is found that the cross sections corresponding to the different noble-gas perturbers are of the same order of magnitude for lower values of the principal quantum number n but become increasingly different from each other with increasing n and for n=13 and 14 the difference approaches two orders of magnitude. Qualitatively, the n-dependence of the cross sections is similar to that obtained in the studies of the l-mixing collisions in the Rydberg states of the alkali-metal atoms. The results are compared with those predicted by the existing theoretical models. Good agreement is obtained for He and Ne perturbers with the results of calculations by Sirko et al. in which the Fermi pseudopotential and perturbation approach were employed.