Half-life of 51Mn.

The half-life of 51Mn was measured by serial gamma spectrometry of the 511-keV annihilation photon following decay by β + emission. Data were collected every 100 seconds for 100,000-230,000 seconds within each measurement (n = 4). The 511-keV incidence rate was calculated from the 511-keV spectral peak area and count duration, corrected for detector dead time and radioactive decay. Least-squares regression analysis was used to determine the half-life of 51Mn while accounting for the presence of background contaminants, notably 55Co. The result was 45.59 ± 0.07 min, which is the highest precision measurement to date and disagrees with the current Nuclear Data Sheets value by over 6σ.