Investigation of complex ionization amplitudes in cadmium by (e,2e) spectroscopy

Abstract

High-resolution (e,2e) energy spectra are presented which enable the isolation of interference effects between J =0, 1,2 multipoles in electron-impact ionization of cadmium. It is found that both resonant and nonresonant processes are important. Relative magnitudes and phases of ionization amplitudes are obtained which disagree with plane-wave Born approximation calculations.

e, 2e angular distributions and energy spectra in cadmium

“…More recently, Martin et al (1994) obtained a series of high-resolution (e, 2e) energy spectra which enable the isolation of interference effects between J = 0, 1, 2 multipoles in electronimpact ionization of cadmium. The kinematic conditions corresponded to those of the earlier angular distribution measurements, with momentum transfer K ≈ 0.2 atomic units.…”

“…The energy dependence of the coefficients b J reflects the presence of both direct ionization and autoionization. Details of the model calculations are given in Martin et al (1994); here it is noted that the b J contain energy independent complex multipole amplitudes.…”

“…Of interest here is the (e, 2e) spectral pair for 2.5-4.5 eV ejected electrons in the binary and recoil peaks (θ = 0 and 180 • ), due to 150 eV incident electrons scattered through +3 • . Figure 4 (top panel), taken from Martin et al (1994), shows the sum of the binary and The vertical bars at 0.012 eV intervals represent the statistical uncertainty after binning three data points taken at 0.004 eV intervals. Labels refer to 4d 9 5s 2 5p autoionizing levels.…”

“…The 5p 2 widths are from matrix elements calculated at the 5p6p configuration average energy; these differ somewhat from the local values. From Martin et al (1994).…”

“…On the other hand, if the kinematics are such that a particular model can be used to analyse the data, it is possible to restrict the range of angles at which (e, 2e) energy spectra need to be taken. This approach has been adopted by recent experiments in cadmium (Martin et al 1994), which were carried out at intermediate incident beam energy and small momentum transfer K. Good-resolution, high-quality (e, 2e) energy spectra were measured at a few carefully chosen ejected-electron angles. It was found that the (e, 2e) energy spectra were well described by a very restricted set of partial wave amplitudes; this enabled experimental values to be obtained for (relative) individual partial wave amplitude magnitudes and phases.…”