The half-life of thorium C′

Abstract

1. The half-life of Th C′ was determined by a new method of coincidence technique.2. Previous investigators have recognized difficulties in regard to this investigation. These were: (a) random delays in the counters; (b) coincidences due to other disintegrations; (c) possibility of difference in delays in recording α- and β-particles. In this investigation the difficulties arising from these effects have been overcome.3. From this type of experiment it is possible to determine the order in which the particles are emitted.4. It would appear that the time of breakdown of a counter depends slightly upon the magnitude of the initialionization.5. The value for the half-life of Th C′ was found to be 3.0 ± 0.15 × 10−7 sec.

The half-life of $$^{212}$$Po

“…The β and α pulses have slightly different rise time (τ R , defined as a time interval of the (10-90)% rising edge): τ R = 2.44(16) ns for β particles and τ R = 2.31( 14) ns for α particles (see Insets in Fig. 5) 5 . The τ R values were calculated for β and α signals with amplitudes in the energy interval 700-1050 keV (in the energy scale of β particles).…”

“…A fit of the obtained time distribution returns the half-life value T 1/2 = 295.09 (26) ns in agreement with the value T 1/2 = 295.10(26) ns obtained with the method described above. 5 Rise time of scintillation detector depends on several factors: photodetector sensitivity and time properties, the readout electronics bandwidth, scintillation material, size and geometry of the scintillator and reflector, energy and ionization density of particle (see, e.g., [37][38][39]). The difference in the rise time for α and β particles observed in the present study can be explained by their different energy distributions and ionization densities.…”

“…Gaseous counters have been used in the early experiments [3][4][5][6][7][8] to detect the β particle emitted in the 212 Bi decay and the subsequent α particle of 212 Po. Combinations of scintillation and semiconductor detectors were utilized in the experiments [9,10,12,13], with β and α particles from an external source (where the BiPo sequence of decays occurred) registered by the detectors.…”

The half-life of $^{212}$Po

“…Experimental technique / Compilation Half-life, ns (year) [3] (1939) Geiger-Müller counters, external source 300(100) [4] (1943) Geiger-Müller counters, external source 260(40) [5] (1948) Geiger-Müller counters, external source 300(15) [6] (1949) Geiger-Müller and proportional counters, external source 304(4) [7] (1949) Geiger-Müller counters, external source 220(10) [8] (1953) Geiger-Müller and proportional counters, external source 290(10) [9] (1962) Plastic scintillators, external source 305(25) [10] (1963) CsI(Tl) and plastic scintillators, external source 305(5) [11] (1972) Source in liquid scintillator 302(6) 1 [12] (1975) Plastic scintillator, surface barrier Au-Si detector, external source 296(2) [13] (1981) Surface barrier Au-Si and HP-planar Ge detectors, external source 309(11) [14] (8) ns reported in Ref. [11].…”

“…6 too. The approach allows to eliminate an amplitude dependence of the pulse-time origin, which appears in the simple low-level-discriminator algorithm 5 .…”