How to measure ultra short half life or lifetimes of radioisotopes?
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Ultra short half life or life time of radioisotopes in the range of 10 -9 -10 -15 sec can be estimated by two techniques using Doppler-shift methods, Recoil Distance Plunger Method (RDPM or RDM) and Doppler Shift Attenuation Method (DSAM). The two techniques are rather different, but Both the techniques rely on the Doppler effect. Doppler effect is the the shift in energy of a γ-ray when it is emitted from a moving source. In Gist A γ -ray detector was used to view a narrow region of space at a given distance away from a thin target foil. γ -Rays from recoiling, excited nuclei that decayed in the region viewed by the detector were recorded as a function of distance from the target to obtain a decay curve. A knowledge of the recoil velocity or velocity distribution allowed the nuclear lifetime to be calculated. Spacial resolution and inadequate knowledge of the recoil velocity distribution limited the accura...
