Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of Physics B Atomic and Molecular Physics

Exchange and direct mechanisms in heteronuclear alkali Penning ionisation

M. T. Djerad, M. Chéret, F. Gounand

Published Aug 14, 1987• 4 citations
Publisher

Abstract

The authors measure rate coefficients for Penning ionisation occurring in a vapour mixture of rubidium and potassium at thermal energy. The experimental technique uses the mass spectrometry analysis of collisional currents resulting from continuous laser excitation of the atoms. They report the first experimental evidence concerning the non-occurrence of an exchange-type mechanism. Although a second exchange-type reaction cannot be discarded by their experimental results, it seems that Penning ionisation, involving low-lying excited alkali atoms, most probably proceeds via the direct mechanism.

DOI
10.1088/0022-3700/20/15/025

Related papers

Penning and associative ionisation of highly excited rubidium atoms

M. Chéret, L. Barbier, W. Lindinger +1 more

Highly excited and resonant states are created in a rubidium vapour in order to study the collisional ionisation with the ground state and between these different excited species. A mass analysis allows one to separate the atomic and molecular channels. Penning ionisation with a resonant state is shown to have a great efficiency (rate coefficient greater than 10 -8 cm 3 s -1 ) for all the highly excited levels under study (6d, 8s, 7d). The associative ionisation rate coefficient between these excited atoms and a ground-state atom lies in the expected range 10 -10 to 5*10 -10 cm 3 s -1 and seems to be independent of l j and values.

Journal of Physics B Atomic and Molecular Physics•Oct 14, 1982•63 citations

Electronic mechanisms of Penning ionization involving excited alkali atoms

M. T. Djerad, F. Gounand, Anil Kumar +1 more

Penning ionization (PI) occurring during the collision of a Rydberg atom Rb(nl) with a resonant state K(4P) or Rb(5P) is analyzed theoretically. By using a semiclassical approach, we calculate the rate coefficients corresponding to both the direct and exchange decay channels. We implement the method by deriving various approximations for the exchange and direct decay widths. The radiative mechanism is found to dominate the thermal-energy quenching of alkali atoms by PI, the exchange being negligible. The calculated values are in reasonable agreement with the available experimental results.

The Journal of Chemical Physics•Dec 1, 1992•7 citations

Experimental study of Penning and Hornbeck-Molnar ionisation of rubidium atoms excited in a high s or d level (5d⩽nl⩽11s)

L. Barbier, M. Chéret

Rb + and Rb 2 + formation in a laser-excited Rb vapour is extensively studied for s and d levels ranging from 5d to 11s levels. Collisional ionisation with a ground-state atom leads to Rb 2 + formation by Hornbeck-Molnar reaction with rate coefficients lying in the 10 -10 cm 3 s -1 range. This reaction is analysed theoretically. Penning ionisation occurs in collision with a resonant-state atom, Rb(5p), with a high efficiency (rate coefficient above 10 -8 cm 3 s -1 ). Associative ionisation between the 7s level and the 5p level is also observed (rate coefficient about 10 -10 cm 3 s -1 ). This reaction appears negligible for the neighbouring 5d level.

Journal of Physics B Atomic and Molecular Physics•Mar 26, 1987•61 citations

Hornbeck-Molnar ionisation in a K-Rb mixture

M. T. Djerad, M. Chéret, F. Gounand

Rate coefficients for Hornbeck-Molnar ionisation in a K-Rb mixture at thermal energy are measured using CW laser excitation of the atoms. Special attention is paid to the formation of the KRb + molecular ion in Rb(nl)-K(4S) and K(nl)-Rb(5S) collisions. The absolute rate constant values are deduced from the analysis of collisional currents by mass spectrometry techniques. They are compared with the theoretical values calculated using a model recently developed by Janev and Mihajlov (1980).

Journal of Physics B Atomic and Molecular Physics•Aug 14, 1987•9 citations

Theoretical interpretation of Penning and associative ionisation in collisions between two excited rubidium atoms

L. Barbier, A. Pesnelle, M. Chéret

Associative and Penning ionisation cross sections, rho AI and rho PI are calculated for collisions of two excited atoms Rb(nl)+Rb(5p 2 P 3 2/) in the classical impact parameter formulation for nl=5d to 9d and 7s. It is shown that the very large Penning ionisation rate constants, measured by the authors and presented earlier, can be well explained by such a model in terms of direct and exchange autoionisation widths, as well as the associative ionisation contributions which have been observed to be quite different for ns and nd cases.

Journal of Physics B Atomic and Molecular Physics•Mar 26, 1987•11 citations

Reverse energy pooling in a K-Na mixture

G. De Filippo, S. Guldberg-Kjær, Slobodan Milošević +2 more

We report experimental rate coefficients for the reverse heteronuclear energy-pooling collisions $\mathrm{K}(5D)+\mathrm{Na}(3S)\ensuremath{\rightarrow}\mathrm{K}(4P)+\mathrm{Na}(3P)$ and $\mathrm{K}(7S)+\mathrm{Na}(3S)\ensuremath{\rightarrow}\mathrm{K}(4P)+\mathrm{Na}(3P)$ at thermal energies. Both reactions are exothermic and very high rates were observed showing that reverse exothermic energy-pooling is an order of magnitude more efficient than the corresponding forward endothermic energy-pooling reactions. This is in accordance with the general behavior of the exothermic and endothermic energy-pooling rate coefficients in alkali-metal atoms. In the experiment the potassium atoms were excited in two steps to either the $5D$ or $7S$ state via the $4P$ level using two broadband cw dye lasers. A double-modulation technique has been used to select the fluorescence contributions at the $\mathrm{Na}{(3P}_{J})$ exit channels due only to the above reactions. The ground-state sodium and potassium atom densities were measured by the absorption of lines from a K-Na hollow-cathode lamp. The measured densities and fluorescence intensities have been used to obtain absolute reverse energy-pooling rate coefficients. The contribution to the rate coefficients from other processes are discussed.

Physical Review A•Jan 1, 1998•8 citations
The authors measure rate coefficients for Penning ionisation occurring in a vapour mixture of rubidium and potassium at thermal energy. The experimental technique uses the mass spectrometry analysis of collisional currents resulting from continuous laser excitation of the atoms. They report the first experimental evidence concerning the non-occurrence of an exchange-type mechanism. Although a second exchange-type reaction cannot be discarded by their experimental results, it seems that Penning ionisation, involving low-lying excited alkali atoms, most probably proceeds via the direct mechanism.
Highly excited and resonant states are created in a rubidium vapour in order to study the collisional ionisation with the ground state and between these different excited species. A mass analysis allows one to separate the atomic and molecular channels. Penning ionisation with a resonant state is shown to have a great efficiency (rate coefficient greater than 10 -8 cm 3 s -1 ) for all the highly excited levels under study (6d, 8s, 7d). The associative ionisation rate coefficient between these excited atoms and a ground-state atom lies in the expected range 10 -10 to 5*10 -10 cm 3 s -1 and seems to be independent of l j and values.
Penning ionization (PI) occurring during the collision of a Rydberg atom Rb(nl) with a resonant state K(4P) or Rb(5P) is analyzed theoretically. By using a semiclassical approach, we calculate the rate coefficients corresponding to both the direct and exchange decay channels. We implement the method by deriving various approximations for the exchange and direct decay widths. The radiative mechanism is found to dominate the thermal-energy quenching of alkali atoms by PI, the exchange being negligible. The calculated values are in reasonable agreement with the available experimental results.
Rb + and Rb 2 + formation in a laser-excited Rb vapour is extensively studied for s and d levels ranging from 5d to 11s levels. Collisional ionisation with a ground-state atom leads to Rb 2 + formation by Hornbeck-Molnar reaction with rate coefficients lying in the 10 -10 cm 3 s -1 range. This reaction is analysed theoretically. Penning ionisation occurs in collision with a resonant-state atom, Rb(5p), with a high efficiency (rate coefficient above 10 -8 cm 3 s -1 ). Associative ionisation between the 7s level and the 5p level is also observed (rate coefficient about 10 -10 cm 3 s -1 ). This reaction appears negligible for the neighbouring 5d level.
Associative and Penning ionisation cross sections, rho AI and rho PI are calculated for collisions of two excited atoms Rb(nl)+Rb(5p 2 P 3 2/) in the classical impact parameter formulation for nl=5d to 9d and 7s. It is shown that the very large Penning ionisation rate constants, measured by the authors and presented earlier, can be well explained by such a model in terms of direct and exchange autoionisation widths, as well as the associative ionisation contributions which have been observed to be quite different for ns and nd cases.
We report experimental rate coefficients for the reverse heteronuclear energy-pooling collisions $\mathrm{K}(5D)+\mathrm{Na}(3S)\ensuremath{\rightarrow}\mathrm{K}(4P)+\mathrm{Na}(3P)$ and $\mathrm{K}(7S)+\mathrm{Na}(3S)\ensuremath{\rightarrow}\mathrm{K}(4P)+\mathrm{Na}(3P)$ at thermal energies. Both reactions are exothermic and very high rates were observed showing that reverse exothermic energy-pooling is an order of magnitude more efficient than the corresponding forward endothermic energy-pooling reactions. This is in accordance with the general behavior of the exothermic and endothermic energy-pooling rate coefficients in alkali-metal atoms. In the experiment the potassium atoms were excited in two steps to either the 5D5D5D or 7S7S7S state via the 4P4P4P level using two broadband cw dye lasers. A double-modulation technique has been used to select the fluorescence contributions at the Na(3PJ)\mathrm{Na}{(3P}_{J})Na(3PJ​) exit channels due only to the above reactions. The ground-state sodium and potassium atom densities were measured by the absorption of lines from a K-Na hollow-cathode lamp. The measured densities and fluorescence intensities have been used to obtain absolute reverse energy-pooling rate coefficients. The contribution to the rate coefficients from other processes are discussed.