Observation of resonance structure in the Na − photodetachment cross section

We have used a collinear laser-ion beam apparatus to investigate the partial cross section for the photodetachment of Na{sup {minus}} via the Na(4s)+e{sup {minus}}({epsilon}p) channel. The measured cross-section spectrum is compared to a recent {ital R}-matrix calculation [C.-N. Liu and A. F. Starace, preceding paper, Phys. Rev. A {bold 59}, 3643 (1999)]. The photodetachment cross section was measured in the energy range 4.657{endash}4.880 eV. In this spectrum, we have identified four resonances that converge on the Na(4d) threshold. The energies and widths of the resonances were determined from the measured cross section. A semiempirical formula has also been used to predict the positions of the four resonances and to show that, in a semiclassical model, the resonances belong to the same {sup 1}P{sup o} series. {copyright} {ital 1999} {ital The American Physical Society}