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Walter, C. W.; Gibson, N. D.; Bilodeau, R. C.; Berrah, N.; Bozek, John D.; Ackerman, G. D.; Aguilar, Alejandro

doi:10.1103/physreva.73.062702

Cited by 28 publications

(41 citation statements)

References 39 publications

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“…The primary decay mechanism is tunneling through the barrier, and thus the width and strength of the resonances are influenced by the particular form of the potential. This resonance behavior has been reported for other inner-shell photodetachment studies, such as in Li − [33][34][35][36], B − [22,37,38], C − [39][40][41], and Fe − [19]. As a consequence of their decay mechanism, the resonances are broad structures in the photodetachment cross section and since they are often located very close to a threshold, the corresponding Wigner threshold behavior is severely altered by their presence, as pointed out by [47]).…”

Section: Cross Section (Mb)supporting

confidence: 78%

Inner-shell photodetachment fromRu−

et al. 2010

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Inner-shell photodetachment from Ru − was studied near and above the 4p excitation region, 29-to-91-eV photon energy range, using a merged ion-photon-beam technique. The absolute photodetachment cross sections of Ru − ([Kr] 4d 7 5s 2 ) leading to Ru + , Ru 2+ , and Ru 3+ ion production were measured. In the near-threshold region, a Wigner s-wave law, including estimated postcollision interaction effects, locates the 4p 3/2 detachment threshold between 40.10 and 40.27 eV. Additionally, the Ru 2+ product spectrum provides evidence for simultaneous two-electron photodetachment (likely to the Ru + 4p 5 4d 6 5s 2 state) located near 49 eV. Resonance effects are observed due to interference between transitions of the 4p electrons to the quasibound 4p 5 4d 8 5s 2 states and the 4d → εf continuum. Despite the large number of possible terms resulting from the Ru − 4d open shell, the cross section obtained from a 51-state LS-coupled R-matrix calculation agrees qualitatively well with the experimental data.

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Section: Cross Section (Mb)supporting

confidence: 78%

Inner-shell photodetachment fromRu−

et al. 2010

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“…Apart from the double photodetachment, that was considered for other light ions in previous studies [7,8,[10][11][12][13], we here also report the triple photodetachment in the photon energy range of K-shell excitation and ionization. Two K-shell ionization thresholds were identified and the corresponding threshold energies were determined.…”

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confidence: 83%

“…To test and better understand the theoretical prediction of such cascades, we performed extremely comprehensive quantum calculations for the formation of the intermediate resonances and for the complex deexcitation pathways at a level of detail never attempted before. In particular, all resonance parameters (resonance energy, natural line width, and strength) of the 1s 2s 2 2p 6 photoionization resonance as well as the (absolute) cross sections and ion yields are determined independently by experiment and multi-configuration Dirac-Fock (MCDF) calculations.Previous experimental studies of double detachment via inner K-shell excitation/ionization were performed for several anions lighter than O − , i.e., for Li − [7,8], B − [10], and C − [11,12]. A recent review of related computations is provided in Ref.…”

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confidence: 99%

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Prominent role of multielectron processes inK-shell double and triple photodetachment of oxygen anions

et al. 2016

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The photon-ion merged-beams technique was used at a synchrotron light source for measuring absolute cross sections of double and triple photodetachment of O − ions. The experimental photon energy range of 524-543 eV comprised the threshold for K-shell ionization. Using resolving powers of up to 13000, the position, strength and width of the below-threshold 1s 2s 2 2p 6 2 S resonance as well as the positions of the 1s 2s 2 2p 5 3 P and 1s 2s 2 2p 5 1 P thresholds for K-shell ionization were determined with high-precision. In addition, systematically enlarged multi-configuration Dirac-Fock calculations have been performed for the resonant detachment cross sections. Results from these abinitio computations agree very well with the measurements for the widths and branching fractions for double and triple detachment, if double shake-up (and -down) of the valence electrons and the rearrangement of the electron density is taken into account. For the absolute cross sections, however, a previously found discrepancy between measurements and theory is confirmed. Negative atomic ions play an important role in lowtemperature plasmas such as the upper atmosphere or the interstellar medium [1] and also in technical applications. For example, in the context of antihydrogen production, it has been proposed to use an ensemble of laser-cooled anions as a coolant for antiprotons [2]. Negative ions are fundamentally different from neutral atoms or positive ions since the extra electron in a negative ion is not only bound by the long-range Coulomb interaction with the atomic nucleus but, more importantly, also by a short-range attractive force due to the polarization of the atomic core. The accurate theoretical description of these ions still challenges the state-of-the-art quantum computations although the numbers of their bound states are generally finite. The low-excitation levels of negative ions are readily accessible by laser spectroscopy (see, e.g., [3][4][5][6]). Therefore, this technique has been a prime source of experimental information about the mutual interactions among the valence electrons.A sensitive tool for studying the interactions between the valence and the core electrons is inner-shell ionization of negative ions [7,8]. Here, we apply the photon-ion merged-beams technique (see [9] for a recent overview) to determine the absolute cross sections for double and triple ionization (detachment) of oxygen anions in the photon energy range 524-543 eV. In this energy range, a K-shell vacancy may be produced either by direct ionization of an initial 1s electron or via the formation of a resonance state by exciting one 1s electron to a higher shell such as 2p. In either case, the K-vacancy decays subsequently by a cascade of radiative and nonradiative processes leading to a distribution of final charge states with O + and O 2+ as the most prominent charged reaction products. To test and better understand the theoretical prediction of such cascades, we performed extremely comprehensive quantum calculations for the formation...

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“…The J f =5/2 resonance state is very close to the neutral threshold. It is known that a shape resonance close to threshold appears asymmetrical [6,[35][36][37][38] and should therefore have a small line shape parameter. The reported line shape parameter for peak B in [17] is the smallest among all of the observed peaks, which is consistent with its being a shape resonance near threshold.…”

Section: Resonance Statementioning

confidence: 99%

Experimental and theoretical study of bound and quasibound states ofCe−

Walter

Gibson

et al. 2011

Phys. Rev. A

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The negative ion of cerium is investigated experimentally with tunable infrared laser photodetachment spectroscopy and theoretically with relativistic configuration interaction in the continuum formalism. The relative cross section for neutral atom production is measured with a crossed ionbeam-laser-beam apparatus over the photon energy range 0.54 -0.75 eV. A rich resonance spectrum is revealed near threshold, with at least twelve peaks observed due to transitions from bound states of Ce − to either bound or quasi-bound excited states of the negative ion. Theoretical calculations of the photodetachment cross sections enable identification of the transitions responsible for the measured peaks. Two of the peaks are due to electric-dipole-allowed bound-bound transitions in Ce − , making cerium only the second atomic negative ion that has been demonstrated to support multiple bound states of opposite parity. In addition, combining the experimental data with the theoretical analysis determines the electron affinity of cerium to be 0.628(10) eV and the fine structure splitting of the ground state of Ce − ( 4 H 7/2 -4 H 9/2 ) to be 0.09775(4) eV.

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Shape resonance inK-shell photodetachment fromC−

Cited by 28 publications

References 39 publications

Inner-shell photodetachment fromRu−

Inner-shell photodetachment fromRu−

Prominent role of multielectron processes inK-shell double and triple photodetachment of oxygen anions

Experimental and theoretical study of bound and quasibound states ofCe−

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