COHERENT CORRELATION ENHANCEMENT OF OUTER SHELL PHOTOIONIZATION CROSS-SECTIONS OF ALKALI-LIKE IONS

An alkali-like ion interaction with inner electrons of an alkali-like ion leads to a significant increase in the photoionization cross secti on of the outer s electron. This occurs not only for ground state ions with one s electron in the outer shell, but also when the outer s ele ctron is in an excited state. The reason for this amplification, in ad dition to coherent enhancement in summing of the correlation amplitude s, is that the zero in the direct amplitude occurs below threshold. Th is leads to a constructive interference with the correlation amplitude above the photoionization threshold, in contrast to a destructive int erference in the case of a neutral atom with the same electronic confi guration, for which the zero occurs above threshold.