Author: Stanley Gerald Thompson

Publisher:

Published: 1950

Total Pages: 10

ISBN-13:

The recent production by Thompson, Ghiorso, and Seaborg of a radioactive isotope of berkelium (atomic number 97) makes it possible to investigate the chemical properties of this transuranium element by means of the tracer technique. This isotope has been prepared through the bombardment of Am241 with about 35 Mev helium ions in the 60-inch cyclotron of the Crocker Laboratory and is believed to have the mass number 243, or possibly 244. This Bk243 has a half-life of 4.6 hours and decays by electron capture with about 0.1% branching decay by alpha-particle emission. In the present tracer chemical experiments, the radiations accompanying the electron capture process were used as a means of detection and were counted in two ways. Where the sample deposits on the platinum plates were essentially weightless, as was the case following the evaporation and ignition of the elutriant solutions in the column adsorption experiments, a high efficiency was obtained by using a windowloess proportional counter to count the Auger electrons. The thicker samples from the precipitation experiments in which carrier materials were used were counted close to the thin window (3 mg/cm2 mica) of a bell type Geiger counter filled with 10 cm. xenon to enhance the efficiency for counting the x-rays. An aluminum absorber of thickness about 20 mg/cm2 was used between the sample and counter window to reduce errors due to variable absorption of soft components caused by small differences in sample thickness.