2007/02/28 by A. C. Hayes, J. L. Friar · 1 citation
Physics and Astronomy · #nucl-th
paper · pdf · doi:10.1016/j.physletb.2007.05.021
published as Phys.Lett.B650:229-232,2007 · 4 Pages, no figures
arxiv created 2007/05/02 · arxiv updated 2009/12/01
There exist in nature a few nuclear isomers with very low (eV) excitation energies, and the combination of low energy and narrow width makes them possible candidates for laser-based investigations. The best candidate is the lowest-energy excited state known in nuclear physics, the 7.6(5) eV isomer of 229Th. A recent study suggests that a measurement of the temporal variation of the excitation energy of this isomer would have 5-6 orders of magnitude enhanced sensitivity to a variation of the fine structure constant (α≅ 1/137.036) or of a strong interaction parameter (mq/ΛQCD). We reexamine the physics involved in these arguments. By invoking the Feynman-Hellmann Theorem we argue that there is no expectation of significantly enhanced sensitivity to a variation in the fine structure constant (beyond that obtained from experimental considerations such as the low energy and narrow width of the isomer). A similar argument applies to the strong interaction, but evaluating the shift due to temporal variations of the underlying parameters of the strong interaction may be beyond current nuclear structure techniques.