Inner-shell photodetachment from N i − : A giant Feshbach resonance

Inner-shell photodetachment from Ni-([Ar] 3d(9)4s(2)) leading to Ni+, Ni2+, andNi(3+) ion production was studied near and above the 3p excitation region, in the 60-90 eV photon energy range, using a merged ion-photon beam technique. The absolute photodetachment cross section of Ni- leading to Ni+ ion production was measured. The 3p -> 3d photoexcitation in Ni- gives rise to a giant Feshbach resonance. In the near-threshold region, a Fano profile, modified by aWigner s-wave (l = 0) threshold law, accurately fits the Ni- single-photodetachment cross section. A lower-order R-matrix calculation shows overall agreement with essential features of the experimental data, confirming the nature of the strong, asymmetric Fano profile of the giant 3p -> 3d photoexcitation-autodetachment resonance in Ni-.