Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

Fermi to Gamow-Teller mixing ratios in the nuclear beta decays of /sup 58/Co and /sup 56/Co

Thesis/Dissertation ·
OSTI ID:6244755
The Fermi to Gamow-Teller mixing ratios, y = C/sub v/M/sub f//Ca/sub A/M/sub GT/, in the isospin-hindered beta decays (..delta..J = 0, T = /sup + -/1) of /sup 58/Co and /sup 56/Co have been accurately determined from extensive and detailed studies of the directional distributions of beta rays and gamma rays emitted from oriented /sup 58/Co and /sup 56/Co nuclei. The cobalt nuclei were oriented in a thin foil of permendur (49% Co, 49% Fe, and 2% V) magnetically saturated at ultralow temperatures (10/sup -20/K). Beta-ray and gamma-ray spectra were measured, with a Si(Li) detector and a Ge(Li) detector respectively, at four different angles with respect to the nuclear orientation axis. The gamma-ray background in the beta-ray spectra is removed by means of a mechanical shutter. The beta-ray asymmetries and the gamma-ray anisotropies were determined independently at each angle by normalizing the cold (approx. = 10/sup -20/K) spectra by the corresponding warm (4.2/sup 0/K) spectra taken at the same angle. Necessary corrections made on the beta-ray spectra due to the various experimental effects are described in detail. The experimental beta-ray asymmetries after the proper corrections were found to be in very good agreement with the theoretical expectations over a wide energy region. Including all estimated systematic errors, the beta-ray asymmetry parameters, A/sub ..beta../, were determined to be A/sub ..beta..//sup 58/ = 0.341 +- 0.020 for /sup 58/Co and A/sup 56/ = 0.352 +- 0.015 for /sup 56/Co. The Fermi to Gamow-Teller mixing ratios y corresponding to these A/sub ..beta../'s are y/sup 58/ = -0.005 +- 0.012 for /sup 58/Co and y/sup 56/ = -0.086 +- 0.008 for /sup 56/Co. The obtained result of y/sup 56/ is in very serious disagreement with the latest measurement.
Research Organization:
Columbia Univ., New York (USA)
OSTI ID:
6244755
Country of Publication:
United States
Language:
English