Photodetachment of He- 1s2s2p P-4(0) in the region of the 1s threshold - art. no. 012714

The photodetachment cross section of the 1s2s2p P-4(0) metastable state of He- in the region of the 1s threshold has been calculated using our enhance d R-matrix code with the asymptotic part upgraded to handle a negative-ion system. The results show a 1s photodetachment cross section with numerous s tructures, completely different from similar situations in atoms or positiv e ions. This is found to be due to the dominance of correlation of both ini tial and final states of the negative ion. Specifically, interchannel coupl ing and a newly identified multiconfiguration overlap effect are primarily responsible for the dramatic 1s photodetachment cross-section phenomenology . Comparison with a previous calculation has been made and, while there are some areas of excellent agreement, overall there are very serious discrepa ncies, as much as an order of magnitude.