In the optical, each photon generates a single electron. However, in the near UV, shortward of ~3200 Å there is a finite probability of creating more than one electron per UV photon (see Christensen, O., J. App. Phys. 47,689, 1976). At room temperature the theoretical quantum yield (i.e., the number of electrons generated for a photon of energy E > 3.5eV (~3500 Å)), is Ne = E(eV)/3.65. The HRC CCDs quantum efficiency curve has not been corrected for this effect. The interested reader may wish to see the
STIS Instrument Handbook
for details on the signal-to-noise treatment for the STIS CCDs.
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