New results from pionic atoms

In the last few years the resolution of Ge- and Si-detectors has been improved remarkably, particularly for low energetic X-rays. It therefore became possible to measure absorption broadenings and transition energies of pionic 2p-1s transitions in very light elements, which could be measured before with only limited accuracy. In a recently performed measurement of the pionic 2p-1s transitions in /sup 6/Li, /sup 7/Li and /sup 9/Be a small Ge- and a small Si- detector were used with resolutions of better than 550 eV below 50 keV and better than 200 eV below 10 keV, respectively. The broadening Gamma /sub 1S/ of the pionic 1s level due to strong interaction between the orbiting pion and nucleus was measured with an accuracy of 10-20 eV, corresponding to an error of less than 5%. The shift of the binding energy of the pion in the 1s level Delta E/sub 1s/, due to strong interaction, was determined to an accuracy of 15 eV, corresponding to an error of less than 5% for Li and around 0.5% for Be. For the calibration of the system, muonic lines, adjacent to the pionic lines were used. The energies of these monic lines are easily calculated. The resolution of the spectrometer was calibrated using the same muonic lines. (5 refs).