CROSS-SECTIONS, POLARIZATION AND ORIENTATION IN ELECTRON-IMPACT EXCITATION TO NE-ASTERISK(2P(5)3P) STATES

This work reports results from a comprehensive experimental and theore tical study of the electron-impact excitation of some levels belonging to the (2p(5)3p) configuration in neon. We performed electron-polariz ed photon coincidence experiments for the excitation of the 3p'[3/2](2 ) 3p[3/2](2), 3p[5/2](2) and 3p[5/2](3) levels in neon where the polar ized photon emitted in the Ne(2p(5)3p) --> Ne*(2p(5)3s) radiative dec ay was detected in coincidence with the scattered electron. We report experimental results for the Stokes parameters P-i (i = 1,2, 3, 4), fo r an incident electron energy of E = 80 eV in the electron scattering angular range of 22 degrees-70 degrees, and for E = 50 eV for the angl e of 22 degrees, thus supplementing results reported earlier for this energy for the angular range 30 degrees-70 degrees. We also report her e theoretical distorted-wave approximation (DWA) and first-order many- body theory (FOMBT) results for the same excitations and electron ener gies for the integral cross sections (ICSs), for differential cross se ctions (DCSs). and for Stokes parameters. Our theoretical results are compared with all available experimental results. A detailed discussio n and some conclusions with respect to the physics involved in the exc itation processes considered here are then presented. We also give a t heoretical discussion about the nature of the information that can be obtained about the collision process by analysing the experimental dat a. In particular, in this study we found both experimentally and numer ically that the angular momentum transferred to the target, L-perpendi cular to, as a function of electron scattering angle is the same, with in experimental error, for the states with total angular momentum J = 2.