Experimental and theoretical study of electron-impact ionization of atomic ions in the Sm isonuclear sequence

AICHELE, K.; ARNOLD, W.; HATHIRAMANI, D.; SCHEUERMANN, F.; SALZBORN, E.; MITNIK, D. M.; GRIFFIN, D. C.; COLGAN, J.; PINDZOLA, M. S.

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

The American Physical Society

Año: 2001 vol. 64 p. 52706 - 52716

1050-2947

Experimental measurements and theoretical calculations of absolute cross sections are carried out for the electron-impact ionization of atomic ions in the Sm rare-earth-metal isonuclear sequence. Absolute cross sections for Smq+ ions for q=1-12 were measured using the electron-ion crossed-beam technique and calculated with the configuration-average distorted-wave method for the charge states q=4-12. The theory includes both direct ionization and excitation-autoionization contributions, and includes transitions from both ground and metastable levels. We present the cross sections in an electron-impact energy range from threshold up to 1000 eV for all Sm ions up to Sm12+. These systems are extremally complex, but the configuration-average method, when combined with statistical averaging of the cross sections over the many levels, provides results that are in overall good agreement with the experimental measurements. The single-ionization cross sections are dominated by contributions from indirect mechanisms of excitation-autoionization in the low-energy region.