Mesonic Atoms: Radiative Yields of theπ-MesonLSeries

Abstract

The total radiative yields of the $L$ series from $\ensuremath{\pi}$-mesonic atoms have been measured for most of the elements $_{5}\mathrm{B}$ through $_{33}\mathrm{A}$s. The yield curve has a broad maximum of \ensuremath{\sim}70% in the region $12\ensuremath{\lesssim}Z\ensuremath{\lesssim}16$ and decreases at both higher and lower $Z$ values. This decrease is presumably due to competition from direct nuclear absorption at the higher $Z'\mathrm{s}$ and to nonradiative processes at the lower $Z'\mathrm{s}$. The yields are fairly constant for $25\ensuremath{\lesssim}Z\ensuremath{\lesssim}30$, suggesting a possible magic number effect at $Z=28$. The rapid decrease in yield with decreasing $Z$ cannot be attributed to competition between the simple Auger effect and radiative transitions. The simple Auger transition probabilities are about 40 times smaller than the observed values. More complex nonradiative processes are probably involved, such as those proposed by Day and Morrison.