arXiv subjects

David J. Pegg

Publications and source records attributed to David J. Pegg.

4 recordsLinked to original sources

arXiv2012

Threshold photodetachment in a repulsive potential

We report on the first experimental observation of a new threshold behavior observed in the 5g partial channel in photodetachment of K-. It arises from the repulsive polarization interaction between the detached electron and the residual K(5g) atom, which has a large negative dipole polarizability. In order to account for the observation in the K(5g) channel, we have developed a semiclassical model that predicts an exponential energy dependence for the cross section. The measurements were made with collinear laser-ion beams and a resonance ionization detection scheme.

physics.atom-ph↗

arXiv1997

Photodetachment study of the 1s3s4s ^4S resonance in He^-

A Feshbach resonance associated with the 1s3s4s ^{4}S state of He^{-} has been observed in the He(1s2s ^{3}S) + e^- (εs) partial photodetachment cross section. The residual He(1s2s ^{3}S) atoms were resonantly ionized and the resulting He^+ ions were detected in the presence of a small background. A collinear laser-ion beam apparatus was used to attain both high resolution and sensitivity. We measured a resonance energy E_r = 2.959 255(7) eV and a width Γ= 0.19(3) meV, in agreement with a recent calculation.

physics.atom-ph↗

arXiv1997

Resonance structure in the Li^- photodetachment cross section

We report on the first observation of resonance structure in the total cross section for the photodetachment of Li^-. The structure arises from the autodetaching decay of doubly excited ^1P states of Li^- that are bound with respect to the 3p state of the Li atom. Calculations have been performed for both Li^- and H^- to assist in the identification of these resonances. The lowest lying resonance is a symmetrically excited intrashell resonance. Higher lying asymmetrically excited intershell states are observed which converge on the Li(3p) limit.

physics.atom-ph↗

arXiv1997

Electron affinity of Li: A state-selective measurement

We have investigated the threshold of photodetachment of Li^- leading to the formation of the residual Li atom in the $2p ^2P$ state. The excited residual atom was selectively photoionized via an intermediate Rydberg state and the resulting Li^+ ion was detected. A collinear laser-ion beam geometry enabled both high resolution and sensitivity to be attained. We have demonstrated the potential of this state selective photodetachment spectroscopic method by improving the accuracy of Li electron affinity measurements an order of magnitude. From a fit to the Wigner law in the threshold region, we obtained a Li electron affinity of 0.618 049(20) eV.

physics.atom-ph↗