47 research outputs found
The FERRUM project: radiative lifetimes of the 3d(5)(S-6)4s4p(P-3)y P-6 degrees states of FeII measured with time-resolved vacuum ultra-violet laser spectroscopy
We report on lifetime measurements of the 3d(5)(S-6)4s4p(P-3)y P-6 degrees states of Fe II using time-resolved vacuum ultraviolet (VUV) laser spectroscopy. A laser-produced plasma has been used as the source of free Fe+ ions. The tunable VUV radiation was obtained employing resonantly enhanced sum-difference four-wave-mixing of short laser pulses. We obtained tau((6)P(3/2)degrees) = 3.90(20) ns, tau((6)P(5/2)degrees) = 3.80(20) ns and tau((6)P(7/2)degrees) = 3.65(20) ns
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.Comment: 4 pages, 2 figure, 19 references, RevTeX, figures in ep
Photodetachment study of He^- quartet resonances below the He(n=3) thresholds
The photodetachment cross section of He^- has been measured in the photon
energy range 2.9 eV to 3.3 eV in order to investigate doubly excited states.
Measurements were made channel specific by selectively detecting the residual
He atoms left in a particular excited state following detachment. Three
Feshbach resonances were found in the He(1s2p ^3P)+e^-(epsilon p) partial cross
section: a ^4S resonance below the He(1s3s ^3S) threshold and two ^4P
resonances below the He(1s3p ^3P) threshold. The measured energies of these
doubly excited states are 2.959260(6) eV, 3.072(7) eV and 3.26487(4) eV. The
corresponding widths are found to be 0.20(2) meV, 50(5) meV and 0.61(5) meV.
The measured energies agree well with recent theoretical predictions for the
1s3s4s ^4S, 1s3p^2 ^4P and 1s3p4p ^4P states, respectively, but the widths
deviate noticeably from calculations for 1s3p^2 ^4P and 1s3p4p ^4P states.Comment: 10 pages, 3 figures, LaTeX2e scrartcl, amsmath. Accepted by Journal
of Physics B; minor changes after referee repor
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
Isotope shift in the electron affinity of chlorine
The specific mass shift in the electron affinity between ^{35}Cl and ^{37}Cl
has been determined by tunable laser photodetachment spectroscopy to be
-0.51(14) GHz. The isotope shift was observed as a difference in the onset of
the photodetachment process for the two isotopes. In addition, the electron
affinity of Cl was found to be 29138.59(22) cm^{-1}, giving a factor of 2
improvement in the accuracy over earlier measurements. Many-body calculations
including lowest-order correlation effects demonstrates the sensitivity of the
specific mass shift and show that the inclusion of higher-order correlation
effects would be necessary for a quantitative description.Comment: 16 pages, 6 figures, LaTeX2e, amsmat
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