J.S. Thompson

The production of Ca− through sequential charge exchange with Li vapor

Abstract The efficiencies for producing Ca − through sequential charge exchange between Ca + projectiles and Li vapor have been measured for the first time. The measurements were made over a projectile energy range of 20 to 100 keV under experimental conditions commensurate with tandem accelerator applications. Production efficiencies in terms of negative ion charge state fractions versus projectile energy, Li vapor cell temperature and Li target density were determined for negative ion formation within a detection window α of ±11 mrad. Within this range of angular divergence, the efficiency for production is observed to be an increasing function of the projectile energy even at the highest energies used during the measurements (100 keV). The results of these measurements as well as a description of the experimental apparatus and techniques utilized are presented.

Angular distributions of electrons photodetached from the B− ion

A crossed-beams apparatus has been used to measure, for the first time, the angular distributions of electrons photodetached from B− ions. The angular dependent yields of the ejected photoelectrons were determined using energy-and angle-resolved electron spectroscopy. The asymmetry parameter was found to be essentially constant at β 0.18 over the spectral range 1.78–2.09 eV

Energy- and angle-resolved photoelectron spectroscopy of negative ions

Energy- and angle-resolved photoelectron detachment spectroscopy is currently being used to investigate the structure of negative ions and their interaction with radiation. Measurements of the electron affinity of the Ca atom and the partial cross sections for photodetachment of the metastable negative ion, He− (1s2s2p 4P), are reported.

Photodetachment of He−: Angular distributions of photoelectrons

Energy‐ and angle‐resolved photoelectron detachment spectroscopy has been used to study the spectral dependence of the angular distributions of electrons photodetached from a beam of He− ions.

Photodetachment of metastable He

Abstract A crossed-beams apparatus has been used to measure angular distributions and cross sections for photoelectron detachment from metastable He − . Energy- and angle-resolved electron spectroscopy was used to investigate the spectral dependences of the angular distribution of the photoelectrons. The angular distributions along with photoelectron yield measurements were used to determine the cross sections for photodetachment of He − (2 4 P) via the energy resolved He(2 3 P) and He(2 3 S) exit channels. The precision of the cross section measurements was enhanced by exploiting the kinematic effects associated with detachment from a fast beam source. Calculated cross sections for the photodetachment of H − were used to establish an absolute scale for the He − cross section measurements.

Angular distributions of electrons from the photodetachment of metastable He

Energy- and angle-resolved photoelectron spectroscopy has been used to investigate the spectral dependences of the angular distributions of electrons photodetached from a beam of metastable He- ions.

Autodetachment spectroscopy of metastable negative ions

Abstract This paper is a review of some of our recent measurements on the metastable negative ions, Be− and He2−, using the technique of fast-beam autodetachment spectroscopy.