Shape resonances in the absolute<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>K</mml:mi></mml:mrow></mml:math>-shell photodetachment of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mi mathvariant="normal">B</mml:mi><mml:mo>−</mml:mo></mml:msup></mml:mrow></mml:math>

Berrah, N.; Bilodeau, R. C.; Dumitriu, I.; Bozek, John D.; Gibson, N. D.; Walter, C. W.; Ackerman, G. D.; Zatsarinny, Oleg; Gorczyca, T. W.

doi:10.1103/physreva.76.032713

Cited by 24 publications

(23 citation statements)

References 54 publications

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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: 82%

“…However, the non-sequential emission of two or more electrons is expected to mostly contribute to the decay of negative oxygen, whose decay width is in very good agreement with experiment. We note that a similar, not yet understood discrepancy be-tween theoretical and experimental resonance strengths still remains for the K-shell detachment of B − [10] and the K-shell ionization of O + [21]. Closer inspection of the electron emission from the doubly excited intermediate states as recently performed for the photoionization of Xe 5+ ions [28] may in the future shed more light on this remaining discrepancy.…”

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confidence: 99%

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

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“…The experimental technique has been described previously [18][19][20][21][22]. A 7.54-keV negative-ion beam of Ru − was produced using a cesium sputter source (SNICS II, from NEC) [23], with an ion current of about 40 nA obtained in the interaction region after shaping and spatial trimming.…”

Section: Experimental Methodsmentioning

confidence: 99%

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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“…Soon after, the method of laser photodetachment threshold spectroscopy was developed [2][3][4][5] together with techniques of photodetachment electron spectroscopy, 6 of which the photodetachment microscope is a prominent case. 7 Synchrotron light sources have enabled studies of inner shell photodetachment processes 8 and high power lasers make it possible to investigate negative ions in intense laser fields. 9 Recently, the first high resolution bound-bound single photon spectroscopy was successfully carried out on the Os − ion.…”

Section: Introductionmentioning

confidence: 99%

Ion optical design of a collinear laser-negative ion beam apparatus

Diehl

Wendt

Lindahl

et al. 2011

Review of Scientific Instruments

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An apparatus for photodetachment studies on atomic and molecular negative ions of medium up to heavy mass (M ≃ 500) has been designed and constructed. Laser and ion beams are merged in the apparatus in a collinear geometry and atoms, neutral molecules and negative ions are detected in the forward direction. The ion optical design and the components used to optimize the mass resolution and the transmission through the extended field-free interaction region are described. A 90° sector field magnet with 50 cm bending radius in combination with two slits is used for mass dispersion providing a resolution of M∕ΔM≅800 for molecular ions and M∕ΔM≅400 for atomic ions. The difference in mass resolution for atomic and molecular ions is attributed to different energy distributions of the sputtered ions. With 1 mm slits, transmission from the source through the interaction region to the final ion detector was determined to be about 0.14%.

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Shape resonances in the absoluteK-shell photodetachment ofB−

Cited by 24 publications

References 54 publications

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

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

Inner-shell photodetachment fromRu−

Ion optical design of a collinear laser-negative ion beam apparatus

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