Application of the Coincidence Method to Testing the Lifetime and Level Scheme of Radium C'


THE application of the coincidence method to investigations of nuclear processes may be extended in certain ways by using a variable resolving time of the coincidence circuit and by measuring pseudo-coincidences, that is, counts arising from two impulses which are not simultaneous but separated by a very short time. The number of ‘coincidences’ given by two particles, in which one follows the second in a time determined by the radioactive constant λ is proportional to 1 – e-λτ, τ being the length of the impulse. The duration of the impulse is dependent upon the electrical constants of the circuit, and by changing the constants of one or both circuits it is possible to obtain various determined lengths of the impulses. In order to measure λ, two sets of experiments are made: (a) with the impulse τ1; of the first particle long and of different durations, and the impulse τ2 of the second very short; (b) with the conditions reversed. The difference ab is equal to N1N2/N( e λτ 2 - e λτ 1 ) where N1 and N2 are the number of counts in each counter, N the number of disintegrations. The method of lengthening the impulses only from one kind of particle allows one also to decide the order in which the particles are emitted.

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  1. 1

    Ellis, C. D., International Conf. of Physics, London, 1934.

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ROTBLAT, J. Application of the Coincidence Method to Testing the Lifetime and Level Scheme of Radium C'. Nature 144, 248–249 (1939).

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