MEASUREMENTS OF THE GROUND-STATE IONIZATION-ENERGY AND WAVELENGTHS FOR THE 1S(21)S(0)-1SNP(1)P(1) (N=6-12) LINES OF AL-XII

The wavelengths of the 1s(2) S-1(0)-1snp P-1(1) (n=6-12) transitions i n He-like Al XII have been measured in laser-produced and X pinch plas mas. The accuracy of the present measurements (0.3-0.5 m Angstrom) is a severalfold improvement over previous results. In addition, the reso nance transitions from the 11 P-1(1) and 12 P-1(1) levels of He-like A l XII are observed. Finally, the Rydberg series is used to determine t he ground-state ionization energy of Al XII, with a precision of 50 pa rts per million. This method gives E(ion)=2085.98+/-0.10 eV. These exp erimental results are compared with theoretical data calculated by sev eral different methods.