Improvements on the third generation of electron momentum spectrometer

Abstract

The significant modifications to our recently constructed electron momentum spectrometer have been implemented. Compared with our previous report, the energy and the angle resolutions are significantly improved and reach ΔE = 0.45 eV, Δθ = ±0.53° and Δφ = ±0.84°, respectively. Moreover, the details of data reduction and the relation between azimuthal angle range and the sensitivity are discussed.

Vibrational effects on the electron momentum distributions of valence orbitals of formamide

“…Detailed descriptions of the spectrometer have been reported previously. 36,37 Using high energy (∼1 keV for atoms and molecules) incident electron beam, electronic structures, especially the ionization energy and the momentum distribution of individual Dyson orbital [38][39][40][41] of the sample molecule can be extracted when the single ionizing collision takes place at Bethe ridge. 15 The kinematics of the incoming and two outgoing electrons can be completely determined through the coincidental measurement.…”

High-resolution electron-momentum spectroscopy of the valence orbitals of the iodine molecule

“…With the standard calibration run for the Ar 3p orbital, the present energy resolution was measured as E = 0.7 eV (full width at half maximum, FWHM) at the impact energy of 1200 eV, and it was slightly better at the impact energy of 600 eV. The azimuthal angle resolution is φ = ± 0.84 • (one standard deviation), and the polar acceptance angle is θ = ± 0.53 • [27]. The energy resolution may slightly deteriorate due to the long measuring period.…”

“…Our spectrometer takes the symmetric noncoplanar geometry in which the two outgoing electrons have nearly the same kinetic energies (E 1 ≈ E 2 ) and the same polar angle θ (θ 1 = θ 2 = 45 • ) [27][28][29]. Therefore, the momentum of the electron before being knocked out can be given through the azimuthal angle φ between the two outgoing …”

“…The details of our high-resolution spectrometer have been reported in previous works [27]. Briefly, the double toroidal energy analyzer equipped with the two-dimensional positionsensitive detectors is used to realize the energy and angle multichannel detection, which greatly enhances the sensitivity of the spectrometer.…”

Ionization-excitation of helium by high-resolution(e,2e)spectroscopy and 4-body distorted-wave calculations

“…The experimental and theoretical works of ionizationexcitation of He have been excellently reviewed by Bellm et al recently [26]. Here, we only briefly summarize the works performed under coplanar or noncoplanar scattering geometry under electron momentum spectroscopy (EMS) conditions of high impact energies and high-momentumtransfer collisions [27][28][29][30][31], which were also used in the present work. The early EMS experiments of the helium ionization and excitation process were performed by Cook et al [18] and Lermer et al [20] at the impact energy 1200 eV.…”