Nuclear Isomeric Transitions of Short Periods

Abstract

THE elements copper, molybdenum, silver, cadmium, indium and lead have been irradiated by a pulsed beam of X-rays, activity ascribable to metastable states being sought in the intervals between pulses. The electrons producing the X-ray pulses had energies up to 1.05 MeV., the pulse width was 5 µsec., repetition frequency 200 per sec. and mean current 15 µamp.; the mean current during the pulse was thus approximately 15 m.amp. The elements were irradiated within Geiger–Müller counters, counts between pulses being displayed on an oscillograph with time-base triggered by the pulses. No evidence of activity was obtained. Periods greater than 100µsec. could have been detected. Some details are given below of the experimental arrangements whereby a particular spurious effect can be eliminated, since these may be of interest in similar studies where more energetic X-rays are available.