INNER-SHELL AND DOUBLE-EXCITATION SPECTRUM OF CESIUM INVOLVING 5P AND6S SUBSHELLS

We report new high resolution observations of the 5p inner shell and o f the doubly excited states of caesium covering the spectral region be tween 600 and 800 Angstrom. The spectra were recorded in the first ord er of a 3 m spectrograph equipped with a 5000 line/mm holographic grat ing. Synchrotron radiation emitted by the 500 MeV electron accelerator served as the background source of continuum. More than 300 new level s of caesium are reported which are interpreted as inner-shell transit ions 5p(6)6s(2)S(1/2) --> 5p(5)6s(P-3(2,1,0) P-1(1))ns, nd and doubly excited transitions 5p(6)6s(2)S(1/2) --> 5p(5)5d(P-3(1,2), F-3(3) and D-3(1))ne. All the observed levels lie well above the first ionization threshold 5p(6)(S-1(0)) and are arranged into Rydberg series convergi ng onto eight conspicuous limits. The interactions of the continuum wi th the discrete levels have been parametrized using the multichannel q uantum defect, theory.