Recoil-distance method

Accurate lifetime measurements by the recoil-distance method... 

Eig. 22 a and b. Determination of lifetime of states of O by recoil-distance method (Devons et al. [2d]), (a) Apparatus for pair emitting and gamma emitting states, (b) Results for 6.13 MeV level. 

The angular correlation between the internal pairs from the [p a 71) resonance at 840 keV was observed by Devons etal, [ 5], and the half-life of the pair emitting level established as (5.0 0.5) X 10 sec by the recoil distance method (Sect. 24). It is clear that the fluorine reactions have provided an unusually extensive amount of information on the properties of the levels involved, but some difficulties remain. Notable among these is the small proton width and consequent low intensity of capture radiation at the 33O and 935 keV levels of Ne o which seem to have the same properties and to show the same (a y) correlations as the 669 keV resonance which gives capture radiation. 

For the measurement of lifetimes of excited states, many efficient methods have been elaborated. Some of the direct methods are electronic timing, recoil distance method, Doppler shift and blocking techniques, yX-ray coincidences and the indirect methods Coulomb excitation, (e,e ) reactions, resonance fluorescence, particle resonance spectroscopy, etc. The methods were reviewed in Berlovich et al. (1972), Nolan and Sharpey-Schafer (1979), FInyes (1986), and others. Using these techniques, it is possible to measure lifetimes in a very wide (>10 s) domain. 

Recent chemical experiments with transactinides have been carried out by application of refined methods. Fast transport is achieved by thermalizing the products of nuclear reactions recoiling out of the target in helium gas loaded with aerosol particles (e.g. KCl, M0O3, carbon clusters) of 10 to 200 nm on which the reaction products are adsorbed. Within about 2 to 5 s the aerosols are transported with the gas through capillary tubes over distances of several tens of metres with yields of about 50%. 

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