X-RAY FROM RADIATIVE ELECTRON-CAPTURE OF HIGHLY-CHARGED HEAVY-IONS INAN ELECTRON COOLER

The x-ray spectra induced by spontaneous capture of free cooling elect rons into bare and hydrogenlike heavy ions have been observed. Au78+, Au79+ and U91+ ions were stored in the storage ring ESR at velocities between 60% and 65% of the velocity of light and the x rays were measu red in coincidence with stored particles having captured one electron in the electron cooler. The lines observed can be attributed to the di rect transition of cooling electrons into the K shell of the projectil e and to the characteristic L-->K transitions. The latter are mainly i nduced by capture into higher shells and subsequent cascade transition s. The measurements are compared to detailed calculations within the f ramework of presently available theories. Although the relative struct ure of the measured spectra is in fair agreement with the theoretical prediction, the total charge-changing rate in the electron cooler is a bout a factor of three smaller than expected.