Electromagnetic Lifetimes of Nuclear Levels by Doppler-Shift and Recoil Methods

Author: Gordon, David Marshall

Year: 1973

Degree: Dissertation (Ph.D.)

Advisor: Kavanagh, Ralph William

Committee Member: Unknown, Unknown

Option: Physics

DOI: 10.7907/RJAY-BF26

Abstract

The Doppler-shift-attenuation (DSAM) and recoil-distance methods have been used to measure electromagnetic lifetimes of nuclear levels in ¹⁶O, ²⁶Al, ³⁰P, ³²P, ³³S, ³⁵Cl, ³⁷Ar, ³⁸K and ⁴⁰K, and the electromagnetic transition strengths deduced from the measured lifetimes have been compared with recent nuclear-model calculations. In addition, measurements have been performed to investigate the existence and magnitude of possible systematic errors in nuclear lifetimes obtained using the gas- stopper version of the DSA technique due to localized heating of the stopping gas by the incident particle beam.

Parameters describing the rate of energy loss of heavy ions in Xe, Ar and He stopping gases have been extracted from DSAM measurements of the γ rays from the decay of the 418-keV level of ²⁶Al, whose lifetime is well known from electronic-timing measurements. In addition, the electronic stopping cross sections for ¹²C and ²⁷Al ions slowing in He and Xe gases were measured for ion energies in the range 560 ≤ E ≤ 2320 keV. Deviations from recent theoretical calculations of electronic stopping power as large as a factor of two have been observed.

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