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A time‐of‐flight spectrometer for measuring inelastic to elastic differential cross‐section ratios for electron‐gas scattering

L. R. LeClair, S. Trajmar, M. A. Khakoo, J. C. Nickel
1996 Review of Scientific Instruments  
We describe a crossed electron beam-atomic beam apparatus which utilizes a pulsed electron gun and field free drift tube to obtain time-of-flight ͑TOF͒ spectra of electrons scattered from atoms and molecules. This apparatus was constructed for the purpose of obtaining inelastic-to-elastic differential cross-section ͑DCS͒ ratios in the energy range extending from threshold to several eV above the threshold of the inelastic channel. The TOF approach eliminates the need for complicated calibration
more » ... licated calibration procedures required when using conventional electrostatic electron energy-loss spectroscopy ͑EELS͒ at these low energies. The characteristics of the apparatus will be given, along with representative TOF spectra from carbon monoxide. From those spectra we obtained DCS ratios at 90°scattering angle for excitation of the a 3 ⌸ state of CO, in the impact energy range of 6-15 eV. These ratios were measured with uncertainties as small as Ϯ4%, which represents a substantial improvement over previous measurements in this energy range. This demonstrates the feasibility of using the TOF technique to measure DCS ratios which in turn can serve as secondary standards to normalize other inelastic DCSs obtained from measurements with EELS.
doi:10.1063/1.1146970 fatcat:apxjpijw2bae3ddfdj4kwrfrpm