The Rb+-Rb collision rate in the energy range of 103-104 K
Abstract
We study both theoretically and experimentally the energy dependence of the low-energy Rb+-Rb total collision rate kia in the energy range from 103 to 104 K. We calculate the integral elastic cross-section and the resonant charge-transfer cross-section by the quantum mechanical molecular orbital close-coupling method, and then obtain kia for temperatures by averaging the cross-sections over a Maxwell-Boltzmann velocity distribution. The experiments are conducted in an ion-neutral hybrid trap, where the Rb+ ions are created by photo-ionization of the cold atoms in a magneto-optic trap (MOT) and accumulated in the linear Paul ion trap. The total ion-atom collision rate kia is measured by monitoring the fluorescence reduction of the steady-state MOT atoms by sequentially introducing photo-ionization and ion-atom collisions. The ion-atom collision energy Ecol ≈ Ti is modified by changing Ti due to Ti being more than six orders of magnitude larger than the Ta of cold atoms. The temperature of ions Ti is obtained by comparing the time-of-flight mass spectrometry of Rb+ from experimental results to that obtained by SIMION simulation. The equilibrium steady Ti is modified by changing the initial root-mean-squared position of the ion cloud, and the kia are measured with Ecol from 8000 to 16 000 K. Both the theoretical and experimental results show that kia increases with Ecol. More specifically, the measured kia increases rapidly with the enlargement of Ecol near 10 000 K. The theoretical calculation results show that kia increases slowly with Ecol. The specific difference may be due to the influence of the ratio of excited states fe on the trend of kia at different Ecol.
- Publication:
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Journal of Physics B Atomic Molecular Physics
- Pub Date:
- July 2020
- DOI:
- 10.1088/1361-6455/ab8b45
- Bibcode:
- 2020JPhB...53m5201L
- Keywords:
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- low-energy ion-atom collision;
- ion-neutral hybrid trap;
- quantum mechanical molecular orbital close-coupling method