Ionization of the N₂3 sigma_gorbital by electron impact studied by asymmetric (e,2e) experiments

Abstract

Absolute triple differential cross sections (TDCS) for the ionization of molecular nitrogen by approximately=300 eV electron impact have been measured in a coplanar asymmetric arrangement. Two different values of the energy loss, Delta E=25.6 and 34 eV, have been chosen in order to investigate the ionization mechanism in an energy region where the resonant channel 3 sigma g to in sigma u, in pi u competes with the direct process. For each Delta E the TDCS have been measured at two momentum transfers, K=0.7 and 0.35 au, in order to approach the dipolar limit. Theoretical models for molecular TDCS are lacking, therefore the present results are qualitatively compared to TDCS of He obtained under analogous kinematics.

Triply differential (e,2e) cross sections for ionization of the nitrogen molecule at large energy transfer

“…A large body of theoretical and experimental works have been reported for EMS studies of molecular targets, see, e.g. [2,4] and references therein, whereas studies concerned with the dynamics of the ionization process of molecules are less numerous [5][6][7][8][9][10][11][12], mainly due to the difficulty in developing a realistic theoretical model to describe this process. However, there has recently been a renewed interest in such dynamics studies, both experimentally [13,14] and theoretically [15][16][17][18][19][20][21].…”

Doubly and triply differential ionization measurements using femtoamp beams of positrons and electrons

“…For recoil interactions (angles larger than 180 • ), within statistical uncertainties no clear differences can be seen between positron and electron impact. Included in the figure are the measurements of Avaldi et al [20], shown by the blue open circles. For comparison purposes, these data have been convoluted with our experimental parameters and normalized to our electron impact binary yields.…”

“…Data are for a projectile scattering angle of 3 • and an energy loss of 28 eV. The present data are compared to the electron impact measurements of Avaldi et al[20] shown by the open blue circles. See text for details.…”

Electron Scattering by Atoms, Ions, and Molecules

“…Comparison between their results obtained in the standard DWBA approach and their molecular 3DW (M3DW) method shows that both calculations reproduce in a satisfactory way the shape of the angular distributions. However, the experimental data of Avaldi et al (1992) are cross-normalized, that is, only a single normalization factor is necessary (and allowed) to put the experimental data on an absolute scale. The figure shows that the M3DW is far superior to the DWBA in reproducing the proper cross normalization.…”

“…The faster of the two outgoing electrons with energy 270 eV is detected at a scattering angle θ a = 3.5 • (a) or θ a = 8.0 • (b), while the detection angle of the slower electron (10.0 eV or 18.4 eV) is varied. The absolute experimental data are fromAvaldi et al (1992). The solid and dashed lines represent the M3DW and DWBA results, respectively, see Section 8.3.5.4, normalized to the experiment at the single point at 295.6 eV where θ a = 3.5 • and θ b = 68 • .…”