4PNP J=0(E)-2(E) AUTOIONIZING SERIES OF CALCIUM - EXPERIMENTAL AND THEORETICAL-ANALYSIS

The even parity 4pnp J = 0, 1, 2 doubly excited autoionizing states of neutral calcium in an atomic beam are investigated by a two-step isol ated core excitation (ICE) method using two different combinations of polarization of the laser beams. The different excited energy levels a re assigned to nine autoionizing Rydberg series 4p(1/2,3/2)nP J = 0, 1 , 2 for 8 less than or equal to n less than or equal to 22. The theore tical interpretation is achieved by a combination of the eigenchannel R-matrix theory and the multichannel quantum defect (MQDT) method. Two , five and six closed interacting channels are introduced for the J = 0, J = 1 and J = 2 series respectively. Theoretical energy level posit ions, autoionization widths and excitation profiles are compared with the experimental data, confirming the identification of the observed s tructures and providing evidence of extended mixing between the 4p(1/2 )np and 4p(3/2)np series.