Auger resonance technique

In other articles in this section, a method of analysis is described called Secondary Ion Mass Spectrometry (SIMS), in which material is sputtered from a surface using an ion beam and the minor components that are ejected as positive or negative ions are analyzed by a mass spectrometer. Over the past few years, methods that post-ion-ize the major neutral components ejected from surfaces under ion-beam or laser bombardment have been introduced because of the improved quantitative aspects obtainable by analyzing the major ejected channel. These techniques include SALI, Sputter-Initiated Resonance Ionization Spectroscopy (SIRIS), and Sputtered Neutral Mass Spectrometry (SNMS) or electron-gas post-ionization. Post-ionization techniques for surface analysis have received widespread interest because of their increased sensitivity, compared to more traditional surface analysis techniques, such as X-Ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES), and their more reliable quantitation, compared to SIMS. 

Ion neutralization (or Ion survival) can dominate this technique. A number of theories have arisen to account for this phenomenon, but all seem to Include both Auger transitions and resonance tunneling processes as the dominant means of Ion neutralization.(4,5) For very slow Ions, as In LEISS, Auger... 

Spectroscopy produces spectra which arise as a result of interaction of electromagnetic radiation with matter. The type of interaction (electronic or nuclear transition, molecular vibration or electron loss) depends upon the wavelength of the radiation (Tab. 7.1). The most widely applied techniques are infrared (IR), Mossbauer, ultraviolet-visible (UV-Vis), and in recent years, various forms ofX-ray absorption fine structure (XAFS) spectroscopy which probe the local structure of the elements. Less widely used techniques are Raman spectroscopy. X-ray photoelectron spectroscopy (XPS), secondary ion imaging mass spectroscopy (SIMS), Auger electron spectroscopy (AES), electron spin resonance (ESR) and nuclear magnetic resonance (NMR) spectroscopy. 

Other spectroscopic techniques used to characterize iron oxides are photoelectron (PS), X-ray absorption (XAS), nuclear magnetic resonance (NMR) (Broz et ah, 1987), Auger (AES) (Seo et ah, 1975 Kamrath et ah, 1990 Seioghe et ah 1999), electron loss (EELS)), secondary ion mass (SIMS) and electron spin resonance (ESR) spectroscopy (Gehring et ah, 1990, Gehring Hofmeister, 1994) (see Tab. 7.8). Most of these tech-... 

Several factors have contributed to this goal in the recent past development of electrochemical techniques for the study of complex reactions at solid electrodes, use of physical methods such as ESCA, Auger, LEED, etc. for the study of surfaces in the ultrahigh vacuum (UHV) environment and in situ techniques under the same conditions as the electrode reaction. Ellipsometry, electroreflectance, Mossbauer, enhanced Raman, infrared, electron spin resonance (ESR) spectroscopies and measurement of surface resistance and local changes of pH at surfaces were incorporated to the study of electrode kinetics. 

Altered surfaces have been inferred from solution chemistry measurements (e.g., Chou and Wollast, 1984, 1985) and from spectroscopic measurements of altered surfaces, using such techniques as secondary ion mass spectrometry (for altered layers that are several tens of nm thick (e.g., Schweda et al, 1997), Auger electron spectroscopy (layers <10 nm thick (e.g., Hochella, 1988), XPS (layers <10 nm thick (e.g., Hochella, 1988 Muir et al, 1990), transmission electron microscopy (TEM, e.g., Casey et al, 1989b), Raman spectroscopy (e.g.. Gout et al, 1997), Fourier transform infrared spectroscopy (e.g., Hamilton et al, 2001), in situ high-resolution X-ray reflectivity (Farquhar et al, 1999b Fenter et al, 2003), nuclear magnetic resonance (Tsomaia et al, 2003), and other spectroscopies (e.g., Hellmann et al, 1997). 

An interesting proposal for cancer therapy using Fe has been made by Mills et al. (81). They have claimed that delivery of Fe-bleomycin to tumor cells followed by photoactivation with 14.4-eV resonant Moss-bauer y rays can produce tumor regression at doses as low as 10" Gy. DNA damage appears to be caused by emission of Auger electrons, which leads to a cluster of positively charged ions and a molecular explosion. It remains to be seen whether this technique is useful only... 

Autoionization spectra resulting from specific resonances can be obtained by electron-electron coincidence measurements (Haak et al. 1984 Ungier and Thomas 1983, 1984, 1985). To associate a fr.rgmentation pattern with a particular core hole excited state and a particular autoionization or Auger decay channel, a double-coincidence experiment must be done using electron impact excitation. The energy of the scattered electron must be determined, the energy of the emitted electron must be detennined, and the ions produced in coincidence with these two events must be determined. The difficulties inherent in these kinds of experiments have been aptly summarized by Hitchcock (1989), If you can do it by photons, don t waste your time with electron-coincidence techniques. ... 

Characterize the material properties of each new generation of complex hydrides to aid in further improvements. Compare different material responses using kinetics experiments coupled with analytic techniques such as X-ray, electron spin resonance (ESR), nuclear magnetic resonance (NMR), Auger spectroscopy, etc. 

A wide variety of other techniques are available for the characterization of supported catalyst systems including X-ray absorption fine structure (EXAFS), Mossbauer, Auger electron. X-ray, and u.v. spectroscopies, magnetic susceptibilities, electron spin resonance spectroscopy, and transmission electron microscopy. However these techniques have not been employed to any significant effect. 

---