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Using magneto-optical traps to measure ion-atom collision cross sections

Todd A. Zimmerman

Jan 1, 20030 citations

Measurement of Electron-Impact Cross Sections using Trapped Rb atoms

M. L. Keeler, Todd A. Zimmerman, John B. Boffard +3 more

APSOct 1, 19990 citations

Use of an atom trap for measuring electron-impact excitation cross sections out of the excited states of rubidium

M. Larsen, Todd A. Zimmerman, John B. Boffard +2 more

APSMay 1, 20020 citations

Electron-atom collisions: From Franck-Hertz experiment to atom traps

Chang-Chun Lin

The key features of the cross sections for electron-impact excitation out of the ground levels of the rare-gas atoms are summarized and application of these cross section data is shown. This is followed by discussions of recent experiments on determination of electron-impact cross sections for excitation out of the metastable levels of He and Ar. The metastiable atom targets are produced by two different methods, i.e., hollow-cathode discharges and charge-exchange collisions of rare-gas ions with Cs atoms. The former method is simple but is limited to low electron energies because of the very small metastable concentration, whereas the latter method yields a fast target beam with predominantly metastable atoms allowing measurements up to the keV range. The measured cross sections show features very different from those of excitation out of the ground levels. Another new development in electron-atom collision is the use of atom traps for measuring ionization cross sections. The experiment is conducted by passing an electron beam pulse through magneto-optically trapped Rb atoms while the trap is momentarily turned off. Turning the trap back on immediately after the electron beam pulse recaptures the unionized atoms allowing only the ions to escape. The ionization cross section is determined bymore » measuring the electron beam current density at the trapped atom region and the fractional loss of trapped atoms due to the electron beam. This method avoids measurements of the absolute number of the target atoms and the overlap between the atomic and electron beams and therefore eliminates the major sources of uncertainty associated with the crossed-beam method for measuring ionization cross section.« lessThe key features of the cross sections for electron-impact excitation out of the ground levels of the rare-gas atoms are summarized and application of these cross section data is shown. This is followed by discussions of recent experiments on determination of electron-impact cross sections for excitation out of the metastable levels of He and Ar. The metastiable atom targets are produced by two different methods, i.e., hollow-cathode discharges and charge-exchange collisions of rare-gas ions with Cs atoms. The former method is simple but is limited to low electron energies because of the very small metastable concentration, whereas the latter method yields a fast target beam with predominantly metastable atoms allowing measurements up to the keV range. The measured cross sections show features very different from those of excitation out of the ground levels. Another new development in electron-atom collision is the use of atom traps for measuring ionization cross sections. The experiment is conducted by passing an electron beam pulse through magneto-optically trapped Rb atoms while the trap is momentarily turned off. Turning the trap back on immediately after the electron beam pulse recaptures the unionized atoms allowing only the ions to escape. The ionization cross section is determined bymore » measuring the electron beam current density at the trapped atom region and the fractional loss of trapped atoms due to the electron beam. This method avoids measurements of the absolute number of the target atoms and the overlap between the atomic and electron beams and therefore eliminates the major sources of uncertainty associated with the crossed-beam method for measuring ionization cross section.« less

Bulletin of the American Physical SocietyMay 1, 19960 citations

Electron Collision Cross-Sections Measured with the Use of a Magneto-Optical Trap

R. Scott Schappe, P Feng, L. W. Anderson +2 more

We present the first application of optically trapped atoms as targets for a scattering experiment. We report absolute total electron scattering cross-sections for ground-state Rb atoms in the range of 7-500 eV.

Europhysics Letters (EPL)Feb 20, 199534 citations

Measurements of ion-atom collision rates within a hybrid trap

Douglas S. Goodman, James E. Wells, Frank A. Narducci +1 more

Bulletin of the American Physical SocietyJun 5, 20140 citations

Methods of Measuring Electron–Atom Collision Cross Sections with an Atom Trap

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