The contribution of the ECC to the forward electron cusp in 50-150 keV amu^-1He⁺-He,Ar collisions

Abstract

The projectile energy dependence of the cross sections for electron capture and for electron loss to the continuum states of the projectiles (ECC and ELC) in 50-150 keV amu-1 He+-He,Ar collisions has been studied measuring the spectra of forward ejected 'cusp' electrons in coincidence with the scattered He+ and He2+ projectiles at five different impact energies. The contribution of the ECC to the forward electron cusp has been found to increase with decreasing projectile energy dominating the forward electron cusp production at 50 keV amu-1 collision energies.

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

“…The eKciency of the particle detector was determined in the same way as in Ref. [2], and was found to be 50 + 3%.…”

“…By integrating the obtained energy spectra in a range corresponding to velocities between 0.9v"and l. lv"(v" is the velocity of the projectile) we determined singly differential cross sections (SDCS's) section values in Eq. (2) were taken from Pedersen et al [9]. We did not measure the thickness of the quenching gas directly, but assumed that it was proportional to the pressure p in the vacuum chamber where the gas cell was located, i.e.…”

“…On the contrary, p and R~c ould be obtained only with large uncertainties (= 30%), due to the fact that Eq. (2) is sensitive to the change of the product pR~, rather than to the separate changes of these parameters. The value 0.23 + 0.07 obtained for the initial metastable fraction f, = p/(1 + p) is in accordance with the value 0.24+ 0.04 measured by Pedersen et al [9] for the production of a neutral helium beam by using a thin neutralization gas of N2 at 300-keV energy.…”

“…The separation of the ELC and ECC processes was the primary goal of an experiment by Kover et al [2], where cusp electrons were measured in coincidence with charge-state selected outgoing projectiles (ejectiles) in He+ on He, Ar collisions. In the experiment by Kover et al [2], cusp electrons in coincidence with neutral ejectiles were also observed.…”

“…The separation of the ELC and ECC processes was the primary goal of an experiment by Kover et al [2], where cusp electrons were measured in coincidence with charge-state selected outgoing projectiles (ejectiles) in He+ on He, Ar collisions. In the experiment by Kover et al [2], cusp electrons in coincidence with neutral ejectiles were also observed. This process can be visualized as a two-electron process, where one electron is transferred into a bound state and a second one into a continuum state of the projectile, and therefore it is called transfer ionization (TI).…”