Disappearance Potential Spectroscopy DAPS

Crossing an ionization threshold means that electrons are lost from the primary beam as a result of ionization of a core hole. Thus if the reflected current of electrons at the primary energy, more usually termed the elastically reflected current, is monitored as a function of energy, a sharp decrease should be observed as a threshold is crossed. This is the principle of operation of DAPS. It is, in a sense, the inverse of AEAPS, and, indeed, if spectra from the two techniques from the same surface are compared, they can be seen to be mirror images. Background problems occur in DAPS also. 

The principal advantages of AEAPS and DAPS over SXAPS is that they can be operated at much lower primary electron currents, thus causing less disturbance to any adsorbed species. 

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Disappearance potential spectroscopy DAPS The EAPFS cross-section is monitored by variations in the intensity of electrons elastically backscattered from the surface. Electronic structure... 

Soft X-ray appearance potential spectroscopy (SXAPS) Disappearance potential spectroscopy (DAPS)... 

D/A DAPS digital-to-analog disappearance potential spectroscopy... 

DAPS Disappearance potential spectroscopy CLS Cathodoluminescence spectroscopy IPES Inverse photoemission spectroscopy BIS Bremsstrahlung isochromat spectroscopy AES Auger electron spectroscopy SAM Scanning Auger microscopy ELS (electron) Energy loss spectroscopy HREELS High-resolution electron energy loss spec-... 

Figure 1 A schematic diagram showing energy levels involved in techniques used to probe unoccupied density of states of a metai. XAS, X-ray absorption spectroscopy BIS, Bremsstrahlung isochromat spectroscopy I PE, inverse photoemission DAPS, disappearance potentiai spectroscopy SXAPS, soft X-ray appearance potentiai spectroscopy and AEAPS, Auger electron appearance potential spectroscopy.

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