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A ring collection spectrometer investigation of the decay of Sb 125 Payne, Frank Alden


A thin-lens beta-ray spectrometer has been modified for collection of beta-rays at the position of the ring focus. This has increased the gathering power/line width ratio from ∽ 0.12 to ∽0.8. The focusing properties of the instrument have been investigated for various geometries. Using the modified spectrometer, the decay scheme of Sb 125 - Te 125 has been investigated. The primary beta spectrum, photoelectron spectra and beta-gamma coincidence spectra have been measured. From conversion coefficient measurements, the following radiative transition multipolarities were determined (energies in kev): 176(E2+M1), 428(E2+M1), 464(E2), 602(E2+M1) and 638(E2). Five primary beta groups have been identified with end point energies of 626, 450, 307, 246 and 133 kev. Previously unobserved transitions of 76, 143, 219, 355, 540 and 640 kev have been identified. Based on all experimental evidence the following states of Te 125 with spin and parity assignments have been proposed: ground state (S1/2+), 36 kev (d₃/2+), 145 kev (h₁₁/₂-), 321 kev (9/2-), 464 kev (5/2+), 525 kev (11/2- or 9/2-), 540 kev (11/2- or 9/2-), 638 kev (5/2+) and 676 kev (spin and parity undetermined).

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