Effects of relativity and “atomic structure” in the KLL Auger spectrum of 88Sr generated in the EC-decay of 88Y

The KLL Auger electron spectrum of 88Sr generated in the EC-decay of 88Y has been analyzed at the instrumental resolution of 11 eV using a combined electrostatic spectrometer. Energies and relative intensities of the all nine transitions were determined and compared with theoretical predictions. Our value of 12067.3(12) eV measured for the absolute energy of the dominant KL2L3(1D2) transition was found to be higher by 7.4 eV (i.e., more than 3σ) than that one obtained in a measurement with external excitation. The discrepancy indicates substantial influence of the “atomic structure effect” on absolute transition energies in our experiment. Very good agreement of the measured 0.14(3) and predicted 0.12 values for the KL1L2(3P0/1P1) Auger transition intensity ratio clearly proved the predicted strong influence of the relativistic effects on the KL1L2(3P0) transition rate even at Z = 38.