Comparison of convoy electron production in ion-atom and ion-solid collisions

Conference · Sat Jan 01 04:00:00 EST 1983

OSTI ID:6127375

Sellin, I A; Breinig, M; Elston, S B; Berry, S D

We begin with an overview for the benefit of participants lacking acquaintance with the subject of convoy-electron production, and continue with highlights of developments occurring since a review and a comprehensive article published in 1982. A sharp cusp in the velocity spectrum of electrons, ejected in ion-atom and ion-solid collisions, is observed when the ejected electron velocity vector v/sub e/ matches that of the emergent ion vector v in both speed and direction. In ion-atom collisions, the electrons primarily originate from capture to low-lying projectile-centered continuum states (ECC) for fast bare or nearly bare projectiles, and primarily from loss to low-lying continuum states (ELC) when loosely bound projectile electrons are available. Most investigators now agree that ECC cusps are strongly skewed toward lower velocities and exhibit full widths half maxima roughly proportional to v (neglecting sometimes strong shell effects). Convoy cusps produced in heavy ion-solid collisions at MeV/u energies are slightly skewed toward high electron velocities, but exhibit velocity-independent widths, very similar to ELC cusp widths. While the shape of the convoy peaks is approximately independent of projectile Z, velocity, and target, dependence on projectile Z as Z/sup 2/ /sup 7/ and energy as E/sup -2/ /sup 2/. Attempts have been made to link convoy electron production to binary ECC or ELC processes, sometimes at the last layer, or alternatively to a solid-state wake-riding model, but our measured dependences of cusp shape and yield on heavy projectile charge state q and energy are inconsistent with available theories. These wake-riding theories seek to explain the origin of convoy electrons in terms of electrons trapped into an oscillatory electron density polarization potential trailing each projectile, which are then liberated at the surface.

• Research Organization: Tennessee Univ., Knoxville (USA); Oak Ridge National Lab., TN (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 6127375
• Report Number(s): CONF-830301-17; ON: DE83009782
• Country of Publication: United States
• Language: English

Related Subjects

640301* -- Atomic
Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATOM COLLISIONS
CATIONS
CHARGED PARTICLES
COLLISIONS
ELECTRIC FIELDS
ELECTRON EMISSION
EMISSION
ENERGY RANGE
HEAVY IONS
HYDROGEN IONS
HYDROGEN IONS 2 PLUS
ION COLLISIONS
ION-ATOM COLLISIONS
IONS
MEV RANGE
MEV RANGE 10-100
MOLECULAR IONS
MULTICHARGED IONS
OXYGEN IONS