Doubly excited levels of alkaline-earth elements near the first ionisation limit. II. Calcium

For pt.I see ibid., vol.15, p.357 (1982). More than eighty unidentified spectral lines are observed by spectroscopic measurements of high-density calcium plasmas generated by an electromagnetically driven shock tube. Half of them are identified in terms of the transitions from doubly excited levels near the first ionisation limit. The energy values of 3d4d 1 P 1 in the singlet system, 3d4d 3 F 2,3,4, 3d4f 3 P 0,2 and 3 D 2,3, and 3d6s 3 D 3 in the triplet system and, tentatively 3d 2 1 D 2 , are determined. The energy values of 3dnp 3 P 2 degrees (n=5 and 6) suggested by previous investigations are altered. A multiplet of the quadrupole transition of 4s4p 3 P degrees -3d4p 3 D degrees and window-type forced (field-induced) autoionisation of 3d5s 3 D are also observed. The position of 3d5s 3 D 3 without the repulsive forces from 4snd 3 D 3 (n>7) is discussed. It is pointed out that the dependence of the widths of the autoionising lines of 3d4p 3 F degrees -3d4d 3 G on electron density agrees with that of non-autoionising lines.