title: Angle-resolving time-of-flight electron spectrometer for near-threshold precision measurements of differential cross sections of electron-impact excitation of atoms and molecules.
abstract: This article presents a new type of low-energy crossed-beam electron spectrometer for measuring angular differential cross sections of electron-impact excitation of atomic and molecular targets. Designed for investigations at energies close to excitation thresholds, the spectrometer combines a pulsed electron beam with the time-of-flight technique to distinguish between scattering channels. A large-area, position-sensitive detector is used to offset the low average scattering rate resulting from the pulsing duty cycle, without sacrificing angular resolution. A total energy resolution better than 150 meV (full width at half maximum) at scattered energies of 0.5-3 eV is achieved by monochromating the electron beam prior to pulsing it. The results of a precision measurement of the differential cross section for electron-impact excitation of helium, at an energy of 22 eV, are used to assess the sensitivity and resolution of the spectrometer.
authors.affiliation: Centre for Antimatter-Matter Studies, Research School of Physical Sciences and Engineering, The Australian National University, Canberra 0200 ACT, Australia. michael.lange@mpihd.mpg.de
authors.forename: M
authors.initials: M
authors.lastname: Lange
authors.forename: J
authors.initials: J
authors.lastname: Matsumoto
authors.forename: A
authors.initials: A
authors.lastname: Setiawan
authors.forename: R
authors.initials: R
authors.lastname: Panajotović
authors.forename: J
authors.initials: J
authors.lastname: Harrison
authors.forename: J C A
authors.initials: JC
authors.lastname: Lower
authors.forename: D S
authors.initials: DS
authors.lastname: Newman
authors.forename: S
authors.initials: S
authors.lastname: Mondal
authors.forename: S J
authors.initials: SJ
authors.lastname: Buckman