Radioactivity ofSc44

Abstract

The decay of Sc 44 has been reinvestigated using a Nal gamma-ray spectrometer and a magnetic-lens spectrometer adapted to coincidence measurements. The main transition from the Sc 44 ground state is to the first excited level of Ca 44 at 1.159±0.003 Mev. The probability for positron emission is 0.932±0.015, in agreement with the theoretical value of 0.928 for an allowed transition (J3max= 1.471=1=0.005 Mev). The conversion coefficients of the 1.16-Mev gamma ray and of the isomeric transition in Sc 44 are 6.3±0.3X10~5 and 0.139±0.003, compatible with E2 and EA transitions, respectively. A weak allowed decay leads to a level in Ca 44 at 2.54±0.03 Mev. The continuous spectrum of low-energy electrons previously reported by J. A. Bruner was found to depend strongly on the thickness of the source and the backing. For the thinnest sources the intensity was found to be \ of that previously reported. Coincidence measurements showed that more than § of the electrons are not coincident with both the positrons and the gamma rays and are, therefore, not emitted in the process of positron decay. It is concluded that there is no indication for a disagreement between the experiment and the theory of atomic excitation during beta decay.f Work supported by the U. S. Atomic Energy Commission. 1 J. A. Bruner and L. M. Langer, Phys. Rev. 79, 606 (1950). 2 Hibdon, Pool, and Kurbatov, Phys. Rev. 67, 289 (1945). 3 P. F. Zweifel, Phys. Rev. 96, 1572(1954. 4 J. A. Bruner, Phys. Rev. 84, 282 (1951).

DISINTEGRATION-RATE DETERMINATION BY 4π-Counting: PART III. ABSORPTION AND SCATTERING OF Β RADIATION

“…They considered t h a t <0.1% of the effect observed could be attributed t o inner bremsstrahlung electrons in the cases of S35 and P3?. This latter observation agrees with recent experimental work (8,40) where inner bremsstrahlung electron emission was found t o occur very much less frequently than reported by Bruner (11 For personal use only.…”

45Sc(α,αn)44Scm+g: a monitor reaction for alpha particle induced reactions

“…The half-lives are very well characterized; the "best" values have changed by not more than 1-2% over the quarter century since the isotope was first studied (13). Errors of 10% in the relative half-lives would be needed to produce a 7% error.…”

“…However, the remarkable accuracy of gamma ray energies, half-lives, and branching ratios reported in ref. 13 make such an assumption unjustifiable. Blue and Bleuler also suggested the spin of the isomer to be 6 + .…”