MEASUREMENTS OF THE GROUND-STATE IONIZATION-ENERGY AND WAVELENGTHS FOR THE 1SNP P-1(1)0-1S(2) S-1(0) (N=4-10) LINES OF O-VII

The wavelengths of the Isnp P-1(1)o-1s(2) S-1(0) (n = 4-10) transition s in He-like O VII have been measured in laser-produced gas puff plasm as. The accuracy of the present measurements (1.5-3.0 m Angstrom) is a large improvement over previous results. In addition, the resonance t ransitions from the 8 P-1(l)o, 9 P-1(1)o, 10 P-1(1)o levels of He-like O VII were observed for the first time. Finally, the Rydberg series i s used to determine the ground-state ionization energy of O vII. This method gives E-ion = 739.35 +/- 0.07 eV. These experimental results ar e compared with theoretical data calculated by different methods.