Photodetachment Resonance in Aluminum

Photodetachment from Al{sup -}(3s{sup 2}3p{sup 2} {sup 3}P) near the threshold to the first excited state of neutral aluminum has been studied. A 19 keV mass resolved Al{sup -} beam was intersected by a frequency-doubled Nd:YAG-pumped dye-laser beam, and the fast atoms created by detachment processes were detected with a channeltron-based detection system. Just below the threshold of the first excited state (3s{sup 2}4s {sup 2}P), a large resonance peak was observed in the detachment signal which is believed to be due to the presence of a doubly-excited, autodetaching negative ion state best described as 3s{sup 2}4snp. A two-electron R-matrix calculation by Liu and Starace generates resonance structure which is qualitatively similar to the data.