Remarks on the Present Status of the Problem of the X-Ray Deficiency inμ-Mesonic Atoms

The $K$ and $L$ x-ray yields from $\mu$-mesonic atoms were recently remeasured by the Chicago group. These results show better agreement with the theoretical predictions than previous measurements, but some discrepancy still persists. It is shown that the problem really reduces to a striking incompatibility between the observed high $K_{\alpha }$ and low $L$ yields in low $Z$ elements (carbon to oxygen). Furthermore, one can show, with the help of theoretical and experimental arguments, that the Auger effect cannot make up for this difference. The crucial problem is, therefore: How is the $2p$ state in carbon and other light elements populated?