Lifetime of the 22S1/2 state in hydrogenlike krypton

We report a measurement of the lifetime of 22S1/2 level in hydrogenlike 84Kr and the first determination of the branching ratio for the M1 decay for this Z=36 one‐electron ion. The lifetime of this state was measured by the beam‐foil time‐of‐flight method, in which the foil was moved relative to a fixed, collimated Si(Li) detector. An analysis based on the single photon spectra from a tightly collimated detector led to the measurements of the lifetime of 22S1/2, the two‐photon emission rate, the M1 emission rate and the branching ratio of M1 decay. All these exprimental results are in good agreement with the theoretical calculations of Parpia and Johnson, and Goldman and Drake.