Angelos K
Dec2-07, 07:50 PM
How do escape peaks occure?
I mean peaks originating from a gamma ray located at the Energy value of \ E_{peak} \equiv E_{gamma}-511KeV.
I read that an annihilation process takes place and one of the annihilation photons escapes detection.To arive at detecting an Energy of E_{peak} the undetected annihilation photon must have had the energy of 511KeV.
Is there any reason why the particle system before annihilation (electron/positron) had a vanishing total momentum, so that two photons of 511KeV were emitted? Why did the incident photon interact with a nucleus in a way such that the produced particle/antiparticle pair had vanishing momentum?
I'd appreciate help.
I mean peaks originating from a gamma ray located at the Energy value of \ E_{peak} \equiv E_{gamma}-511KeV.
I read that an annihilation process takes place and one of the annihilation photons escapes detection.To arive at detecting an Energy of E_{peak} the undetected annihilation photon must have had the energy of 511KeV.
Is there any reason why the particle system before annihilation (electron/positron) had a vanishing total momentum, so that two photons of 511KeV were emitted? Why did the incident photon interact with a nucleus in a way such that the produced particle/antiparticle pair had vanishing momentum?
I'd appreciate help.