Shape of the two-photon-continuum emission from the 1s2s 1 S 0 state in He-like krypton

We report a measurement of the spectral distribution of photons from the two-photon decay of the 1s2s{sup 1}S{sub 0} level in heliumlike krypton. In the experiment, a beam of Kr{sup 34+} ions was excited using a thin carbon foil and the two-photon decays were observed as coincidences in an array of x-ray detectors. An important part of this work was the measurement of the efficiency of the detection system as a function of photon energy. A Monte Carlo model of the experiment was used to compare the data with theoretical calculations and demonstrated good agreement with the nonrelativistic calculations for Z=36. {copyright} {ital 1997} {ital The American Physical Society}