XLVII. Investigation of soft radiations.—VII. Energy expenditure per ion-pair for slow electrons in various gases

Abstract

Summary The proportional counter is applied to the problem of determining the energy expenditure per ion-pair formed in argon, methane, ethylene, air, nitrogen, oxygen and carbon dioxide. Two different methods are applied. In the first the nearly homogeneous X-rays of Copper 64 are employed and the measurement of the number of disintegrations per minute occurring in a known fraction of the source is compared with the ion current through the same tube due to the whole source. Tritium gas is used likewise, in known relative amounts, to give rise to ion-currents and counting rates of easily measurable magnitudes. Hence the energy expenditure is obtained for the photo-electrons produced by Kα X-rays and for the slow β-rays of tritium (average energy=5·7 Kev). The advantages obtained by using slow β-rays in counters are stressed.