Nuclear Level Schemes Research Articles

Radioactivity from Enriched Isotopes of Cadmium

By irradiating in the pile specimens of cadmium enriched in mass 108 and in mass 114, it is possible to interpret more positively the observed radioactivities and to evaluate the gamma-rays associated with each. Cadmium 109 produced by neutron capture in cadmium 108 decays with a half-life of approximately 250 days by $K$-capture to silver 109 in which a strong gamma-ray of 87.5 kev is emitted. Cadmium 115 is isomeric with half-lives of 54 hours and 42.6 days, both isomers decaying to indium 115 by beta-emission. The 54-hour activity yields many gamma-rays in indium whose energies are 335.5, 343.7, 348.9, 369.3, 423.7, 451.9, 525.4, 559.1, and 713.1 kev. These gamma-energies fit well a proposed nuclear level scheme in indium 115.

Absolute Sensitivity of Geiger Counters

THIS subject has, in recent years, become of interest partly (a) in cosmic ray experiments, where information can be gained on the specific ionization of cosmic ray particles (Danforth and Ramsey1), or on shower sizes (Ramsey and Danforth2), and (b) in various applications of the coincidence–counting technique to nuclear physical problems, for example the determination of nuclear level schemes. The latter problem has been admirably discussed by Dunworth3, following work by Feather and Dunworth4.

The Application of the Method of Coincidence Counting to Experiments in Nuclear Physics

The paper describes the principles involved in the application of coincidence counting to problems in nuclear physics, and gives details of the various methods of approach to the solution of nuclear level schemes, with some of the difficulties encountered. It is shown that the maximum source strength which can be used is inversely proportional to the coincidence resolving time and that the method of experiment has the great advantage over most other methods in that it can be used with very weak sources (sources having an activity of about 10−5 millicurie). An accurate knowledge of the absolute net efficiency of a Geiger counter for all types of radiation is required in the interpretation of the coincidence rates, and the method of achieving this at the same time as information is obtained about nuclear level schemes is explained. Further, it is pointed out that the method makes possible a simple and rapid determination of the total energy of disintegration of β-radioactive nuclei and therefore of the mass differences between parent and daughter nuclei.