Towards a measurement of α-decay lifetime variation at high pressure: The case of  ^228Th


We suggest that a change in the lifetime of the α decay of  ^228Th (T_{1/2} = 1.9127(5) yr) may be detected at static pressures as high as 1 Mbar, a regime nowadays achievable in the laboratory by means of diamond anvil cells. The effect is due to the perturbation of the nuclear Coulomb potential and decay Q-value by the electron environment, and is enhanced, in this case, by the high compressibility of Th. The Thomas-Fermi model, within the frame of the Feynman-Metropolis-Teller treatment of the equation of state, has been used for calculations. It is found that at a compression factor of 2 on the volume of the Wigner-Seitz cell, the fractional variation in the lifetime of  ^228Th is about -2 x 10^{-4} (conservative estimate). Detailed experimental procedures to measure this effect by compressing  ^228Th metal in a diamond anvil cell are presented, where diagnostics is based on activity-vs-time recording on suitable lines of the decay γ-spectrum, e.g. the 2.614-MeV peak stemming from the disintegration of the decay product  ^208Tl, at secular equilibrium.

DOI Code: 10.1285/i9788883051302p70

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