J. A. Tanis

Interference effects in electron emission from H2 by 3 and 5 MeV H+ impact

Abstract Interference effects are expected to occur when electrons are emitted coherently within a multi-center molecular field. This phenomenon is analogous to Young’s two-slit experiment. The present work focuses on ionization of H 2 , a molecule composed of two indistinguishable centers, by 3 and 5 MeV H + impact. A parallel-plate electron spectrometer was used to investigate electron emission in the range ∼3–250 eV at observation angles of 30°, 45°, 90°, 135° and 150° with respect to the incident beam. To help identify interference effects, experimental cross-sections were normalized to CDW-EIS calculations for electron emission from two independent H atoms. A sinusoidal-like variation was observed in the normalized electron emission yield for electron energies less than ∼250 eV in general agreement with model calculations.

Inelastic Transmission Of Electrons Through A Single Macro‐Glass Capillary And Secondary Electron Emission

The transmission of electrons with incident energies 300–1000 eV through single glass capillary samples of macroscopic dimensions has been investigated. The transmitted spectra for all energies indicate dominance of inelastic electrons as the tilt angle ψ increases, with the ratio of inelastically to elastically transmitted intensity for tilt angles >2.5° (the indirect region of transmission) reaching a constant value of about 2:1. When the secondary electron emission was analyzed, higher yield was observed with decreasing primary beam energy and with increasing sample tilt angle.

Dependence of electron transmission on charge deposited in tapered glass macrocapillaries at a tilt angle of 5.0

The characteristics of charge deposited (time) into a tapered glass capillary were studied for an incident energy of ? 1025?eV at a tilt angle of 5?. Electron beams resulting in intensities of 1.5?7000?nC deposited into a tapered borosilicate glass capillary were investigated for inlet/outlet diameters of 800/100??m. The electron transmission consisted of stable transmission, fluctuations, blocking and self-discharging associated with a sudden rise of?transmission as deposited charge was ejected from the capillary. In the case of stable transmission, it was found to be due to both elastic and inelastic contributions, with inelastic transmission dominant.

Electron transmission through a single glass macrocapillary: dependence on energy and time

The transmission of electrons through an insulating single cylindrically shaped glass capillary of macroscopic dimensions has been investigated for electron energies from 300 to 1000 eV using a hig ...

X-ray processes associated with projectile charge changing in ~ 1 MeV/u collisions of O5+ on Ar

We are investigating projectile and target x-ray processes associated with projectile electron capture and loss. Processes of interest are resonant-transfer and excitation (RTE) and projectile and target x-ray emission resulting from inner-shell capture. Preliminary measurements have been made for ~ 1 MeV/u O5+ + Ar collisions.

Interferences in electron emission spectra from 1, 3 and 5 MeV H+ + N2collisions

Electron interferences associated with coherent two-centre emission in 1-5 MeV H+ + N2 collisions are investigated. Spectra were measured for ejected electrons with energies from 5-410 eV and observation angles in the range 30° to 150°. Experimental molecular N2cross sections were normalized to theoretical atomic N cross sections, revealing oscillatory structures that do not change significantly with observation angle or collision velocity. It is suggested that the oscillations are due to previously observed secondary interferences arising from intramolecular scattering following ejection of a K-shell electron.

Forward-backward asymmetry in the inelastic scattering of electrons from highly charged ions

Energy-dependent, absolute differential cross sections for 1s2l excitation in F8+ by the scattering of quasi-free target electrons have been measured. The formation and subsequent decay of the F7+ (3lnl´) (n3) doubly excited intermediate states gives rise to a resonant inelastic scattering amplitude which is coherent with the nonresonant inelastic scattering. A strong forward-backward asymmetry was found for the inelastically scattered electrons due to the interference between these two scattering amplitudes. Close-coupling R-matrix calculations show excellent agreement with the experiment and thereby demonstrates a method for obtaining high-resolution, angle-resolved differential inelastic electron-ion scattering cross sections.

Cusp-electron production due to transfer ionization in 25-250 keV/amu He2+ + Ar collisions

Abstract Cusp-electron emission has been investigated in 25–250 keV/amu He2+ on Ar collisions. Two processes which contribute to cusp electrons for this collision system, Electron Capture to the Continuum (ECC) and Transfer Ionization (TI), were distinguished by detecting the electrons in coincidence with the charge-state analyzed outgoing He2+ and He+ projectiles, respectively. The ratios of the electron yields for the TI and ECC channels were determined over the energy range investigated. These ratios can provide information on the role of the electron-electron interaction in the two-electron TI process. The measured TI ECC ratios were compared to the measured total double- to single-bound state capture cross-section ratios. These ratios are found to be consistent with a simple relationship based on the independent particle model, indicating a lack of electron-correlation effects for cusp-electron production by TI in these collisions.

A study of radiative double electron capture in bare chromium ions at the ESR

Radiative double electron capture is a fundamental atomic process which should be observed in collisions of bare ions with atoms, albeit with a much smaller cross-section than single radiative electron capture. A new experiment—to observe this rare process under single-collision conditions—has been performed at the internal gas jet target of the experimental storage ring at GSI in Darmstadt. X-ray spectra associated with single and double charge exchange have been observed in 30 MeV u−1 collisions of bare chromium ions (Cr24+) with helium and nitrogen target gases.

Guiding of electrons through a single glass macrocapillary: investigation of the time dependent transmission

The time dependence of electron transmission through a single, straight glass macrocapillary was investigated for 500-800 eV electrons. We show the time evolution of the transmitted electrons reveals characteristics different from the observation in the case of electron and ion guiding through insulating nanocapillary foils.