Electron capture from alignedp-state Rydberg atoms

Abstract

Electron capture by Li ϩ ions from aligned Na(25p) Rydberg atoms was measured as a function of the approach angle between the alignment axis of the target-atom wave functions and the ion-beam direction, over a range of reduced velocity ṽ ϭ1.0-2.0, where ṽ ϭv ion /v e . A Stark barrel was used to generate uniform rotatable electric fields over the collision volume and to align Rydberg atoms along the field at arbitrary angles over a full range of 360°. A mixture of Na(25p) fine-structure levels was prepared in the Stark barrel by two-step pulsed laser excitation in the presence of a moderate electric field ͑about 56 V/cm͒ followed by adiabatic switching and rotation to 1.8 V/cm. The relative capture cross section, which varied sinusoidally as a function of the alignment angle, had maxima at 0°and 180°and minima at 90°and 270°throughout this velocity range, showing a strong preference for capture from the endwise arrangement. The alignment effect weakened as the projectile velocity was increased. The Rydberg-state results differ in both magnitude and trend from those based on low-lying aligned states. The spin-independent asymmetry parameter was inferred from the angle-dependent capture cross sections after the spin-orbit depolarization effect in the mixed Rydberg p state was fully accounted for so that the results correspond purely to molecular ⌺ and ⌸ collision geometries.

Effect of static electric field on cross sections in antiproton impact ionization of atomic helium

“…The cross section for ionization of hydrogen atom by antiproton collision is determined using the formula [24][25][26][27][28],…”

“…It has been shown to work quite successfully, and in particular, the case of ion-atom collisions at intermediate and low energies in several CTMC applications [25][26][27][28][29][30][31][32][33][34][35][36][37]. Also, it has been widely used for the single valance electron atom target by several workers [25][26][27][28][29][30][31][32][33][34][35][36][37]. In previous works, results were reported not only for single electron targets but also for two and more valence electron targets [34,35] with fairly good agreements of simulated data with other available experimental and theoretical results.…”

“…Therefore, it would be worthwhile to attempt for understanding the effects of the external electric fields on the ionization of helium atoms with antiproton collisions. The Classical Trajectory Monte Carlo (CTMC) method is a well tested method to simulate inelastic ion-atom collision at intermediate energies [25][26][27][28][29][30][31][32][33][34][35][36][37]. The classical similarity [38] and correspondence principle provide the essential base for the classical as well as semiclassical methods such as the Classical Trajectory Monte Carlo, classical over barrier model and semiclassical impact parameter methods, that are able to describe most features [25] of the charge transfer and ionization processes occurring in ion-atom collisions even at low impact velocities.…”

“…The Classical Trajectory Monte Carlo (CTMC) method is a well tested method to simulate inelastic ion-atom collision at intermediate energies [25][26][27][28][29][30][31][32][33][34][35][36][37]. The classical similarity [38] and correspondence principle provide the essential base for the classical as well as semiclassical methods such as the Classical Trajectory Monte Carlo, classical over barrier model and semiclassical impact parameter methods, that are able to describe most features [25] of the charge transfer and ionization processes occurring in ion-atom collisions even at low impact velocities. It has been shown to work quite successfully, and in particular, the case of ion-atom collisions at intermediate and low energies in several CTMC applications [25][26][27][28][29][30][31][32][33][34][35][36][37].…”

“…The classical similarity [38] and correspondence principle provide the essential base for the classical as well as semiclassical methods such as the Classical Trajectory Monte Carlo, classical over barrier model and semiclassical impact parameter methods, that are able to describe most features [25] of the charge transfer and ionization processes occurring in ion-atom collisions even at low impact velocities. It has been shown to work quite successfully, and in particular, the case of ion-atom collisions at intermediate and low energies in several CTMC applications [25][26][27][28][29][30][31][32][33][34][35][36][37]. Also, it has been widely used for the single valance electron atom target by several workers [25][26][27][28][29][30][31][32][33][34][35][36][37].…”