Low-energy electron collisions with sodium: Scattering of spin-polarized electrons

Abstract

The electron-sodium system is a prototype of nonrelativistic electron scattering from a quasi-oneelectron atomic target and is tractable both experimentally and theoretically. Recently, this system has been studied in a series of sophisticated measurements that together approach complete experiments for elastic (3s~3s) and inelastic (3s~3@)scattering. We apply here the theory of orientation and alignment (OA) in atomic collisions to this system using scattering matrices from coupled channel R-matrix calculations described in the first paper in this series [W. K. Trail et al. , Phys. Rev. A 49, 3620 (1994)]. To facilitate the extension of OA theory to other transitions and systems and to clarify its relationship to canonical scattering theory, we present a reformulation in terms of the state spaces identified by a particular scattering event. Following the application of this formulation to paradigmatic OA experiments, we compare our results to those from existing measurements and other theoretical calculations. To contextualize these experiments and aid in identifying promising regions for future measurements, we also present a comprehensive three-dimensional overview of the calculated differential OA parameters for energies from threshold to 8.6 eV.PACS number (s): 34.80.8m, 34.80. Dp, 34.80.Nz 'Present address: trends and structures that distinguish and characterize this system. The cross sections considered in Ref. [1] do not fully describe the physics of e-Na collisions. Until the past two decades, most scattering experiments measured "conventional" diff'erential (DCSs) and/or integrated cross sections (ICSs) that implicitly involve averages over initial and sums over Anal spin and orbital magnetic substates. These necessary averages obscure much of the dynamical information contained in the scattering amplitudes. More recently, however, experiments [2 -17] have become feasible that use a variety of techniques to prepare the target atoms in an initial nonequilibrium distribution of magnetic and/or spin substates or to detect the magnetic and/or spin substates of the results of a scattering event. Such experiments have dramatically increased our understanding of atomic collisions and provide data that test theories at a more fundamental level than was heretofore possible [18 -32].In the present paper, therefore, we extend this inquiry to a class of experiments that uses initial-state preparation and/or final-state analysis to look more deeply into the physics of low-energy e-Na scattering. Rather than DOS's, these experiments measure less familiar quantities snch as exchange asymmetries and triplet-singlet phase angles; the importance of these "orientation and alignment (OA) parameters" rests in their often subtle physical interpretation and in their relationship to the scattering amplitudes for the transitions in questionmatters we shall address in Sec. II. As in Ref.[1], we focus here on scattering from the ground state, considering the two transitions for which data are available: elastic scattering and the...

Angular Momentum Partitioning and Hexacontatetrapole Moments in Impulsively Excited Argon Ions

“…Electron-atom scattering is a prototype of the manybody long-range force problem. Our understanding of collisions with H, He, and the light alkali atoms is good [1][2][3], but calculations of scattering from the heavy noble gases are not yet satisfactory [4][5][6][7][8][9][10]. This is due primarily to the outer p-shell configuration in such atoms and the fact that relativistic effects can be important in certain collision channels.…”