The decay rate of an electron-capture nucleus is proportional to the electron density at the nucleus. To see how the decay rate is changed by artificially, we have measured the half-life of7Be in beryllium(Be) metal at room temperature (T=293 K) and at close to the temperature of liquid helium (T=5 K). We found that the half-life of7Be in Be metal at T=293 K is 53.25 ± 0.04 d, which is slightly longer than those in the hosts of graphite, lithium fluoride and other minerals, surveyed so far. Furthermore, that at T=5 K is 53.39 ± 0.04 d, which is 0.26% longer than that at T =293 K.
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