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Bäckström, Erik; Hanstorp, Dag; Hole, Odd Magnar; Kamińska, Magdalena; Nascimento, R F; Blom, Mikael; Björkhage, Mikael; Källberg, A.; Löfgren, Patrik; Reinhed, Peter; Rosén, Stefan; Simonsson, Ansgar; Thomas, Richard; Mannervik, S.; Schmidt, H. T.; Cederquist, H.

doi:10.1103/physrevlett.114.143003

Cited by 58 publications

(41 citation statements)

References 30 publications

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“…The sum over CSFs in (1) is determined by substitutions of one-electron orbitals from one or more reference states, in this case 1s 2 . .…”

Section: Theoretical Methodsmentioning

confidence: 99%

“…Halogen-like negative ions have recently been investigated [1,7,8]. These have ground states of the form np 5 2 P 3/2 , and the np 5 2 P 1/2 as the only excited states.…”

Section: Introductionmentioning

confidence: 99%

“…A lingering problem [7,8] in these studies seemed to be a disagreement between experimental [1] and theoretical lifetimes from multiconfiguration Hartree-Fock calculations [9], which casts some doubt on the identification of this transition in S − (where n = 3 …”

Section: Introductionmentioning

confidence: 99%

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Resolving a discrepancy between experimental and theoretical lifetimes in atomic negative ions

Brage¹,

Grumer²

2016

J. Phys. B: At. Mol. Opt. Phys.

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Recently the lifetime of the excited 2 P 1/2 -state of S − was measured to be 503 ± 54 s (Bäckström et al. Phys. Rev. Lett. 114, 143003 (2015)). The earlier theoretical lifetime of 436 s was clearly outside the experimental error bars. To investigate this discrepancy we have performed systematic and large-scale multiconfiguration Dirac-Hartree-Fock calculations for this system. After including a careful treatment of correlation and relativistic effects, we predict a well-converged value of 492 s for this lifetime, with an uncertainty considerably less than 1%, thereby removing the apparent conflict between theory and experiment. We also show that this result corresponds to the nonrelativistic limit in the LS-approximation for the M1 transition within this 2 P term. We also demonstrate the usefulness of the latter approach for 2 P transitions in O − , Se − and Te − , as well as for analogous M1 transitions within 2 D terms in Ni − and Pt − ions.

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“…The sum over CSFs in (1) is determined by substitutions of one-electron orbitals from one or more reference states, in this case 1s 2 . .…”

Section: Theoretical Methodsmentioning

confidence: 99%

“…Halogen-like negative ions have recently been investigated [1,7,8]. These have ground states of the form np 5 2 P 3/2 , and the np 5 2 P 1/2 as the only excited states.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Resolving a discrepancy between experimental and theoretical lifetimes in atomic negative ions

Brage¹,

Grumer²

2016

J. Phys. B: At. Mol. Opt. Phys.

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“…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.…”

mentioning

confidence: 99%

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 most advanced set-ups use cryogenic cooling machines to reduce the temperature of their beam guiding vacuum vessels down to values near that of liquid helium [11][12][13][14][15]. On the one hand, this results in a vastly improved residual gas pressure compared to conventional ultra-high vacuum (UHV) set-ups, with correspondingly longer ion storage times [16,17]. On the other hand, storage in such a cold environment allows infra-red-active molecular ions to de-excite to their lowest rovibrational levels prior to starting experiments-a significant improvement over roomtemperature ion-storage facilities [18,19].…”

Section: Introductionmentioning

confidence: 99%

Single-particle detection of products from atomic and molecular reactions in a cryogenic ion storage ring

Krantz

Novotný

Becker

et al. 2017

Nuclear Instruments and Methods in Physics Research Section A:

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We have used a single-particle detector system, based on secondary electron emission, for counting low-energetic (∼ keV/u) massive products originating from atomic and molecular ion reactions in the electrostatic Cryogenic Storage Ring (CSR). The detector is movable within the cryogenic vacuum chamber of CSR, and was used to measure production rates of a variety of charged and neutral daughter particles. In operation at a temperature of ∼ 6 K, the detector is characterised by a high dynamic range, combining a low dark event rate with good high-rate particle counting capability. On-line measurement of the pulse height distributions proved to be an important monitor of the detector response at low temperature. Statistical pulse-height analysis allows to infer the particle detection efficiency of the detector, which has been found to be close to unity also in cryogenic operation at 6 K.

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Storing keV Negative Ions for an Hour: The Lifetime of the MetastableP21/2olevel in<

Cited by 58 publications

References 30 publications

Resolving a discrepancy between experimental and theoretical lifetimes in atomic negative ions

Resolving a discrepancy between experimental and theoretical lifetimes in atomic negative ions

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

Single-particle detection of products from atomic and molecular reactions in a cryogenic ion storage ring

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