Correlational Autodetachment of the Low–Lying Shape Resonances in C^‒, Si^‒ and Ge^‒ photodetachment

The photodetachment cross sections are calculated for the outer np and nearby ns subshells of the C^‒ 2p³⁴S, Si^‒ 3p^{3 4}S and Ge^‒ 4p^{3 4}S negative ions. The prominent interference feature with deep minimum is discovered for the np photodetachment in the vicinity of the ns threshold at omega approximately=6 eV. This structure is due to the strong interaction of the np continuum with the ns to in p shape resonance. This resonance corresponds to the transition of the ns electron to the quasi–bound ‘np’ state with the width Gamma (1 eV). The shape resonance undergoes rapid decay into the np continuum that is analogous to the super–Coster–Kronig transition. The asymmetry parameter for the np photoelectron angular distribution is calculated, showing abrupt changes in the same energy region. The calculations are performed using the spin–polarized version of the random phase approximation with exchange.