Gamma single escape peak

ESCAPE PEAKS Extra peaks often Seen in a gamma spectrum that contains full-energy peaks greater than 1022 key. They are caused by the escape from the detector of one or two annihilation photons of 511 keV each. The single escape peak is at (full-energy -511) keV the double escape peak is at (full-energy -1022) keV. 

SINGLE ESCAPE PEAK An extra peak in a spectrum due to the loss of a 511 keV photon when a high energy gamma-ray is absorbed by pair production. See escape peaks. 

Figure 12.7 presents the spectrum of Na. The single- and double-escape peaks due to the 2.754-MeV gamma are clearly shown. The single- and double-... 

Figure 12.7 A gamma spectrum showing single- and double-escape peaks (from Chap. 4.4.2 of Bertolini and Coche).

Single and double escape peaks from the gamma-rays of greater than 1022keV can be expected. Not all were observed, however. 

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