Single electron ionization of multishell atoms: dynamic screening and post–prior discrepancies in the CDW-EIS model

The effect of multiple ionization on Kα spectra is investigated for aluminum targets irradiated by intense lithium beams. Multiple ionization cross sections have been calculated using a formulation incorporating single-electron ionization probability in the binomial distribution. In contrast to conventional binary-encounter approximation (BEA) theory, the single-electron ionization probabilities for each atomic shell have been calculated using a combination of modified plane-wave Born approximation (MPWBA) and an empirical effective interaction radius which is dependent on both the target ion and the projectile. Our calculations show that the effect of multiple inner-shell ionization on aluminum Kα spectra observed in intense lithium beam experiments is important. Multiple ionization effects become less important as the target ionization state increases. Nevertheless, even for highly ionized species up through Be-like Al multiple ionization effects can be significant and must be considered in the analysis of spectra obtained in intense Li beam-plasma interaction experiments.

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Evaluation of single-electron movies of glutamine synthetase molecules

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075191 ◽

1983 ◽

Vol 41 ◽

pp. 280-281

Author(s):

W. Kunath ◽

E. Zeitler ◽

M. Kessel

Keyword(s):

Electron Microscope ◽

Glutamine Synthetase ◽

Electron Irradiation ◽

Structural Damage ◽

Structural Changes ◽

Single Electron ◽

Continuous Series ◽

Digital Recording ◽

Recording Device ◽

Low Exposure

The features of digital recording of a continuous series (movie) of singleelectron TV frames are reported. The technique is used to investigate structural changes in negatively stained glutamine synthetase molecules (GS) during electron irradiation and, as an ultimate goal, to look for the molecules' “undamaged” structure, say, after a 1 e/Å2 dose.The TV frame of fig. la shows an image of 5 glutamine synthetase molecules exposed to 1/150 e/Å2. Every single electron is recorded as a unit signal in a 256 ×256 field. The extremely low exposure of a single TV frame as dictated by the single-electron recording device including the electron microscope requires accumulation of 150 TV frames into one frame (fig. lb) thus achieving a reasonable compromise between the conflicting aspects of exposure time per frame of 3 sec. vs. object drift of less than 1 Å, and exposure per frame of 1 e/Å2 vs. rate of structural damage.

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Single-electron sensitivity with a lens-coupled CCD camera

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149040 ◽

1993 ◽

Vol 51 ◽

pp. 642-643

Author(s):

G.Y. Fan ◽

Bruce Mrosko ◽

Mark H. Ellisman

Keyword(s):

Focal Length ◽

Thick Layer ◽

Ccd Camera ◽

Single Electron ◽

Bottom Flange ◽

X Rays ◽

Red Phosphor ◽

Ccd Detector ◽

Lens Assembly ◽

Efficient Coupling

A lens coupled CCD camera showing single electron sensitivity has been built for TEM applications. The design is illustrated in Fig. 1. The bottom flange of a JEM-4000EX microscope is replaced by a special flange which carries a large rectangular leaded glass window, 22 mm thick. A 20 μm thick layer of red phosphor is coated on the window, and the entire window is sputter-coated with a thin layer of Au/Pt. A two-lens relay system is used to provide efficient coupling between the image on the phosphor scintillator and the CCD imager. An f1.0 lens (Goerz optical) with front focal length 71.6 mm is used as the collector. A mirror prism, of the Amici type, is used to "bend" the optical path by 90° to prevent X-rays which may penetrate the leaded glass from hitting the CCD detector. Images may be relayed directly to the camera (1:1) or demagnified by a factor of up to 3:1 by moving the lens assembly.

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