Observation of enhanced emission of cusp electrons at impact of excited metastable neutral He projectiles

Abstract

The contribution of excited metastable He projectiles to the production of the forward electron cusp peak has been measured for bombardment of Ar by 400-keV neutral He atoms using the technique of collisional quenching to control the metastable fraction of the beam. The cross section for the production of cusp electrons via target ionization by metastable He atoms has been found to be about 10 times larger than the cross section for the same process for ground-state projectiles. PACS number(s): 34.70.+e Electrons emitted from ion-atom collisions are important messengers of the dynamics of a collision event.Since an emitted electron moves in the field of both nuclei for a relatively long time due to the long-range nature of the Coulomb interaction, these electrons provide theoretical insight into the dynamics of one-electron processes.

Forward electron emission in collisions of He2+ ions with Ar atoms with simultaneous capture of two electrons

“…Such a negative ion state exists at the 2 1 S excitation threshold of He 0 . The mechanism predicted by the model has been verified in a series of subsequent experiments [7][8][9]. Furthermore, cusp was found also in the measurements of the transfer ionization (TI) that leads neutral projectile in the final state for He + projectile ion [5,10,11].…”

Complete break up of ortho positronium (Ps)-hydrogenic ion system

“…(2a)) involving three continuum particles is approximated by the following ansatz in the framework of Coulomb -eikonal approximation [ 24,27,30] (apart from some constants): ) , , ( The two centre effect on the ejected electron from the Ps due to its parent ion (e + ) as well as the screened target ion is implicit in eqn. (7). Since in the final channel all the three continuum particles ( the positron and the two electrons ) are in the long range Coulomb fields of the residual target ion ( He + ), these three interactions are incorporated in eqn (7) .…”

“…(7). Since in the final channel all the three continuum particles ( the positron and the two electrons ) are in the long range Coulomb fields of the residual target ion ( He + ), these three interactions are incorporated in eqn (7) . The justification of the present ansatz for the approximate wave function − Ψ f can be given as follows.…”

“…The relative importance of the above two channels depends on the incident energy as well as on the particular collision system. Study of the angular and energy distributions of these processes provides an unique insight into the collision dynamics and the atomic structures of the collision partners.Since the pioneering experimental discovery [2] of the ELC, a significant number experimental [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] and theoretical studies [18][19][20][21] were performed on the projectile electron loss process (ELC) in different ion-atom, atom -atom collisions. However, until very recently experimental investigations on the ELC process were mostly limited to bare, partially stripped [2-6, 8-12, 17 -21] or neutral [7] heavy projectiles.…”

Breakup of positronium in a collision with aLi+ion

“…Most of the earlier experiments [2][3][4][5][6][7][8][9][10][11] and consequently theories [12][13][14][15][16][17][18][19] on the projectile ionization concentrated on bare , partially stripped [ 2-6, 12, 13, 16-19 ] or neutral heavy projectiles [ 7-11, 14, 15 ] for which a cusp shaped peak was observed in the emitted electron energy spectrum at around e v ( velocity of the electron ) p v ≈ ( velocity of the positron ). This peak was attributed to the electron loss from the projectile ion / atom into its low -lying continuum, usually referred to as the ELP peak .…”