Radioactive Decay of the Neutron

Snell, Arthur H.; Pleasonton, Frances; McCord, R.V.

doi:10.1103/physrev.78.310

Cited by 44 publications

(11 citation statements)

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“…Materials with low absorption cross section for thermal neutrons are used in the construction of the cloud chamber. Very thin Mylar windows at the entrance and exit of the neutron beam from the chamber also reduce the electron background caused by (3).…”

Section: Acknowledgmentsmentioning

confidence: 97%

Decay Properties ofI136

Johnson

O'Kelley

1959

Phys. Rev.

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I 136 , produced from the slow neutron fission of uranium, has been studied with scintillation techniques. From the single-crystal (Nal) and gamma-gamma coincidence spectra, gamma rays were found at energies of 0.20, 0.27, 0.39, 0.46, 0.53, 0.71, 1.00, 1.321 ±0.006, 1.55, 1.72, 1.91, 2.25, 2.40, 2.63, 2.84, and 3.2 Mev. Also, from single-crystal (anthracene) and beta-gamma coincidence measurements, four beta-ray groups were observed with energies of 2.73, 4.23, 5.62, and 7.00 Mev, where the latter represents the I 136 -Xe 136 mass difference and is present in about 6% of the total beta-ray transitions. A partial decay scheme has been proposed, with energy levels in Xe 136 at 1. 32, 2.64, 2.84, 3.03, 3.23, 3.57, 3.74, and 4.20 Mev. The half-life of I 136 was measured as 82.8=bl.5 seconds. In the course of this investigation a source of 3.8-minute Xe 137 was prepared, and was found to emit prominent gamma rays of 0.26 and 0.45 Mev.

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Section: Acknowledgmentsmentioning

confidence: 97%

Decay Properties ofI136

Johnson

O'Kelley

1959

Phys. Rev.

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“…Free neutron beta decay was first observed in 1950 by Snell, Pleasonton, and McCord [19] at the Oak Ridge Graphite Reactor and independently by Robson [20] at the Chalk River reactor in Canada. Both estimated the neutron lifetime to be in the range 10-30 min, consistent with expectation at the time and with the current value.…”

Section: Beam Experimentsmentioning

confidence: 97%

Measurements of the Neutron Lifetime

Wietfeldt

2018

Atoms

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Free neutron decay is a fundamental process in particle and nuclear physics. It is the prototype for nuclear beta decay and other semileptonic weak particle decays. Neutron decay played a key role in the formation of light elements in the early universe. The precise value of the neutron mean lifetime, about 15 min, has been the subject of many experiments over the past 70 years. The two main experimental methods, the beam method and the ultracold neutron storage method, give average values of the neutron lifetime that currently differ by 8.7 s (4 standard deviations), a serious discrepancy. The physics of neutron decay, implications of the neutron lifetime, previous and recent experimental measurements, and prospects for the future are reviewed.

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“…Pulses from the beta detector were accepted if they corresponded to an energy loss of 110 to 610 kev. The protons were detected by the method used by Robson 5 and by Snell, Pleasonton, and McCord, 6 in which the protons are accelerated to about 12 kev in a system that focuses them on the cathode of an electron multiplier. In our case the cathode was an ellipse of Be-Cu 5 in.…”

Section: Measurement Of Betamentioning

confidence: 99%