7 research outputs found
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 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.Comment: 5 pages,6 figures,22 reference
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^- (\epsilon s) 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
\Gamma = 0.19(3) meV, in agreement with a recent calculation.Comment: LaTeX article, 4 pages, 3 figures, 21 reference
Dubbelt exciterade tillstånd i negativa joner
Atomic negative ions are fragile quantum systems in which correlation among the valence electrons plays a very important role. For doubly excited states correlation becomes dominant. Photodetachment is the process where a negative ion absorbs a photon and as a consquence ejects the outermost electron. A new detection scheme has been developed. The residual atom of a photodetachment is state selectively ionised by resonance ionisation spectroscopy. Investigations of the photodetachment threshold of tellurium with neutral particle detection yielded an electron affinity of 1589618(5) m^-1. With state selective detection the Li(2p) photodetachment threshold was investigated and the electron affinity was determined to be 498490(17) m^-1. Resonance structure in the Li^- photodetachment cross section near the Li(3p) threshold has been investigated. According to an assisting calculation this structure is analogous to the symmetrically excited intrashell (_3{0}_3^+)^1P^o state in H^-. In He^- the three doubly excited states, 1s3s4s ^4S, 1s3p^2 ^4P and 1s3p4p ^4P were investigated. The energy positions of all these resonances [1s3s4s ^4S: E_0=(2386803.1+-4.2) m^-1, Gamma=160(16) m^-1; 1s3p^2 ^4P: E_0=2.4782(55)x10^6 m^-1, Gamma=40(3)x10^3 m^-1; 1s3p4p ^4P: E_0=2633297(40) m^-1, Gamma=492(35) m^-1] agree with a recent calculation. The width of the 1s3s4s ^4S resonance agrees with this calculation, but for the 1s3p^2 ^4P resonance there is a slight discrepancy and the 1s3p4p ^4P resonance is only half as broad as predicted