Photodetachment of the H sup minus ion

Conference · Sun Dec 31 23:00:00 EST 1989

OSTI ID:6506658

Quick, Jr, C R; Donahue, J B; Cohen, S ^[1]; Bryant, H C; Tang, C Y; Harris, P G; Mohagheghi, A H; Reeder, R A; Sharifian, H; Toutounchi, H ^[2]; Smith, W W ^[3]

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1. Los Alamos National Lab., NM (USA)
2. New Mexico Univ., Albuquerque, NM (USA)
3. Connecticut Univ., Storrs, CT (USA)

Detachment of electrons from the H{sup {minus}} ion is investigated with an experimental technique whereby an H{sup {minus}} beam moving at a relativistic velocity (2.5 {times} 10{sup 10}cm/sec) is intersected with a fixed frequency laser. The Doppler effect allows systematic variation of the center-of-mass (CM) photon energy over a wide range (factor of 10) by simply adjusting the angle between the ion and laser beams. The focused output from a pulsed, linearly polarized, CO{sub 2} TEA laser operating at 10.6 {mu}m, with peak intensities on the order of 10 GW/cm{sup 2}, was used to examine the multiphoton absorption process in H{sup {minus}}. The fourth harmonic (266 nm) of a ND:YAG laser was used to investigate some of the doubly-excited state resonances in H{sup {minus}}. In the multiphoton absorption work, electron detachment was observed at phonon energies where as few as 2 and as many as 8 photons are required to get above the 1-electron detachment threshold (EDT) of H{sup {minus}} (0.754 eV). Electron yield vs photon energy plots exhibit structure that is laser intensity dependent. Electron yield vs laser pulse energy data was obtained at a few selected CM wavelengths and laser pulse energies. In the single-photon uv laser work, numerous resonances within the H{sup {minus}} photodetachment continuum corresponding to one-photon two-electron excitation processes were observed. The doubly-excited resonances appear to be the Feshbach type. A simple, semi-empirical recursion formula predicts the resonance energy levels. The experimental techniques described here can be used to accurately determine accelerator beam and ion source parameters such as beam energy, energy-spread, and ion density spatial distribution. 7 refs., 5 figs.

• Research Organization: Los Alamos National Lab., NM (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 6506658
• Report Number(s): LA-UR-90-3536; CONF-901116--24; ON: DE91001959
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
ANIONS
AUTOIONIZATION
CHARGED PARTICLES
CROSS SECTIONS
DOPPLER EFFECT
ELECTRON DETACHMENT
ENERGY LEVELS
EXCITED STATES
HYDROGEN IONS
HYDROGEN IONS 1 MINUS
IONIZATION
IONS
LASERS
MULTI-PHOTON PROCESSES
NEODYMIUM LASERS
PHOTOIONIZATION
SOLID STATE LASERS