Fig. (18) Kurie plot of the ¹⁸⁷Re (5/₂⁺) → ¹⁸⁷Os (1/₂^–) β-decay measured with an array of low-temperature microcalorimeters [143]. The least-squares fit of the theoretical spectrum for the first forbidden unique transition yielded a value for χ² per degree of freedom of 0.905. The insert shows the fit of the uppermost part of the β-spectrum and the residuals of the fit in units of a standard deviation.