Experimental study of spin-exchange effects in elastic and ionizing collisions of polarized electrons with polarized hydrogen atoms

Abstract

Alguard, M. J.; Gay, Timothy J. ; Hughes, V. W.; Wainwright, P.F.; Lubell, M. S.; and Raith, W. , "Experimental study of spin-exchange effects in elastic and ionizing collisions of polarized electrons with polarized hydrogen atoms" (1985). Using crossed beams of polarized electrons and polarized hydrogen atoms we have investigated the effect of spin exchange on 90° elastic scattering from 4.4 to 30.3 eV and impact ionization from 14.1 to 197.0 eV. Our results suggest that the range of validity of various theoretical approximation methods is more restricted than had been assumed previously. Using crossed beams of polarized electrons and polarized hydrogen atoms we have investigated the effect of spin exchange on 90" elastic scattering from 4.4 to 30.3 eV and impact ionization from 14.1 to 197.0 eV. Our results suggest that the range of validity of various theoretical approximation methods is more restricted than had been assumed previously. ©1985 The American Physical

A complete numerical approach to electron–hydrogen collisions

“…Though previous quantal calculations [15,94] are consistent with this energy independence, their scatter or insufficient penetration into the threshold region leads to some uncertainty as to the value at threshold. We reproduce our results [39] along with experiment [97] and other calculations for A s in figure 16(b). They confirm a linear, nearly energy-independent behaviour below 0.05 au and that the spin asymmetry approaches the limiting value A s = 0.54 ± 0.01.…”

“…For all the singlet calculations the PECS iterative-coupling method failed to converge and solutions were obtained using our fully-coupled method (n g = 1). However, the energy perturbation method did converge over a useful range of energies, allowing solutions to be obtained for E 0.0025 au below [94], RMPS and CCC [15] calculations and measurements of Fletcher et al [97] and Shah et al [98] are also shown. E = 0.05 au and E 0.0050 au above E = 0.05 au.…”

A polarized atomic hydrogen beam

“…All dimensions shown are in mm such a manner that the spins are adiabatically rotated [6] and maintained either parallel or antiparallel to the direction of the beam by the 100 mG longitudinal magnetic field that is present at the center of the interaction region. A circular aperture 6.0 mm in diameter and located 38 mm upstream from the center of the interaction region serves to define the dimension of the beam.…”

“…Whether used as a probe of the weak interaction [1], as a testing ground for quantum electrodynamics [2], as a laboratory for metrology [3] and .the determination of the values of fundamental constants [4], or as a target for the study of basic atomic coIlisions [5][6][7][8], the hydrogen atom has continued to play a central role in our attempt to understand physical phenomena at their most basic level. As a consequence, much effort has been devoted to the development of atomic hydrogen beams, both ground state and excited state, both polarized and un polarized [9][10][11][12][13][14][15][16].…”

“…Ground-state beams of atomic hydrogen are almost universally generated through the dissociation of hydrogen molecules by dc (Wood's) [18], rf, or microwave discharges [9], or alternatively by thermal methods that employ high-temperature tungsten or tantalum ovens [6,19]. Regardless of the method chosen, each beam design must confront vacuum needs, choice of materials, heating or cooling require-® 2500 Us (1160 -US) Fig.…”