Half-life of the first excited state of 201 Hg

The lifetime of the first excited state of 201Hg, populated by the 201Tl electron capture decay and subsequent g-ray transitions, has been measured for the first time. This measurement has been carried out using a coincidence between an internal conversion electron and a g-ray. The half-life of 81±5 ns has been obtained and B(E2) and B(M1) values were deduced and compared to previous estimates. With these reduced matrix elements, the excitation rate of the first excited state of 201Hg in plasma have been calculated in the frame of a NEET process.