α-decay half-life of ${}^{253}\mathrm{Es}$ in metallic Fe at temperatures between 4 K and 50 mK

It has been claimed recently that half-lives of radioactive nuclei embedded in metals would be significantly affected by electron screening provided by the metal. The effect would further be strengthened at low temperatures. We have determined the half-life-of ${}^{253}\mathrm{Es}$ nuclei embedded in iron at temperatures between 4 K and 50 mK. Our results agree with the room temperature literature value within about 2% and show no dependence on temperature over a range of almost two orders of magnitude.

Figure 1

α-spectrum observed with the ${90}^{°}$ detector. The three rightmost α lines are from ${}^{253}\mathrm{Es}$; the four leftmost ones from ${}^{254}\mathrm{Es}$. The α line used for this work is indicated as line 2.

Figure 2

α-particle count rate ${}^{253}\mathrm{Es}$ in the energy region between 6630 and 6680 keV (see Fig. 1) as a function of time throughout the experiment for the ${90}^{°}$ detector. The blocks of data points that were taken at temperatures of 50 mK, ∼1.2 K, and 4 K are indicated. Highest count rates are obtained at 4 K. The lower count rates at lower temperatures reflect the anisotropic angular distribution that is due to the nuclear orientation (the lowest temperature reached was 50 mK). Superimposed on this is the decay of the ${}^{253}\mathrm{Es}$ source during the time of the measurements.

Figure 3

Half-life fit for ${}^{253}\mathrm{Es}$ at 4 K observed with two of the three α-particle detectors.

Figure 4

Half-life fit for ${}^{253}\mathrm{Es}$ at 50 mK observed with three α-particle detectors.