gested several of the chemical separations. Thanks are also due Mr. Bernie Rossi and the 60-inch cyclotron crew for carrying out the bombardments.
APPENDIX. CHEMICAL PROCEDURETo the solution of Mn in HC1 10 mg amounts of Co, Cu, Fe, Ni, Zn carriers were added. The IN solution was saturated with (NHJsSCN and shaken with a 50 percent mixture of diethyl ether and amyl alcohol. After several washings the alcohol-ether extract was found to be free of Mn. The remaining metals were removed
I. INTRODUCTIONOOTASSIUM 40 is known to decay by beta-and * gamma-ray emission and by electron capture, but recent measurements of the decay constants have been in rather poor agreement. The most reliable recent measurements 1-6 of the beta-half-life have given values ranging from 12.0 to 17.8X10 8 yr., with an average value of about 14.4X10 8 yr. The most ingenious method was that of Stout, 4 who mixed into his potassium sources an accurately known activity of Na 24 , which has nearly the same beta-energy as K 40 , and measured the ratio of K 40 to Na 24 counting rates. Knowing the specific activity of the Na 24 , he was then able to determine the K 40 activity directly, without corrections, and obtained 13.1X10 8 yr.There is even more disparity between the recent estimates of electron-capture intensity, the values ranging from 5 to 190 electron captures per 100 betarays. The discrepancies here can be attributed to the uncertainties inherent in the methods used in making the measurements. The measurement of Bleuler and 1
Two aspects of Ge(Li) gamma-ray spectrometry are discussed. The non-linearity of an amplifier-analyzer system was measured using a precision pulser and was checked with gamma-ray standards. The overall accuracy was 2 parts in 104. The relative detection efficiency of gamma-ray full-energy peaks was determined using sources with well measured relative gamma-ray emission rates. Two Ge(Li) detectors with active volumes of 3 cm 2 × 0.5 cm and 4 cm 2 × 0.5 cm were calibrated in the energy range 80-3200 keV. An overall accuracy of 5 % in the energy region from 500-3200 keV and an accuracy of 10% over the entire range was obtained. The relative areas of the single escape peak and double escape peak to the full energy peak as a function of energy are included. The relative intensities of the 569.6, 1063.6 and 1771 keV gamma-rays following the decay of Z°VBi were measured.
Precision measurements of gamma-ray energies up to 2 MeV were performed using a 2m curved-crystal monochromator. Effectwe source activities of less than 40 mCur were used for the measurements of the transitions in the 2 MeV region. In the 150 keV region, effectxve source actwltles of less than 200 #Cur may be used. Measurements have been performed on the transitions of energies less than 2150 keV which follow the decay of In11~(54 mm), Mn 5n (2.6 h) and Sc 46 (85 d). In addition, results are presented which indicate that the reflection coefficient is approximately hnear with respect to wavelength for the second order reflection from the germanium ( 022) planes m the region of 6-90 m~_ (2000-135 keV). E I RADIOACTIVITY '~Sc, 56Mn, lX6In [from '~Sc, 55Mn, 1151n(n, 7)], I measured E~, I s Natural targets.
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