Structure and dynamics of negative ions

Pegg, D. J.

doi:10.1088/0034-4885/67/6/r02

Cited by 115 publications

(71 citation statements)

References 236 publications

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“…51,52 The broad peak centered around eKE ~0.4 eV is observed in all spectra with photon energies 2.5 < hv < 3.3 eV, although a small red-shift to eKE ~0.2 eV is observed around hv ~2.9 eV. Schiedt and…”

Section: Discussionmentioning

confidence: 83%

Anion Resonances of para-Benzoquinone Probed by Frequency-Resolved Photoelectron Imaging

et al. 2014

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract:The resonant attachment of a free electron to a closed shell neutral molecule, and the interplay between the following electron detachment and electronic relaxation channels represents a fundamental but common process throughout chemical and biochemical systems. The new methodology of anion frequency-resolved photoelectron imaging is detailed and used to map-out molecular excited state dynamics of gas-phase para-benzoquinone, which is the electron accepting moiety in many biological electron-transfer chains. Three-dimensional spectra of excitation energy, electron kinetic energy and electron ejection anisotropy reveal clear fingerprints of excited and intermediate state dynamics. The results show that many of the excited states are strongly coupled, providing a route to forming the ground state radical anion, despite the fact that the electron is formally unbound in the excited states. The relation of our method to electron impact attachment studies and the key advantages, including the extension to time-resolved dynamics and to larger molecular systems is discussed.

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Section: Discussionmentioning

confidence: 83%

Anion Resonances of para-Benzoquinone Probed by Frequency-Resolved Photoelectron Imaging

et al. 2014

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“…In anion PE spectroscopy, and particularly for molecular anions without a permanent dipole moment, the cross-section for electron detachment vanishes at threshold. 32,33 Consequently, these electrons at eKE ~ 0 must arise through indirect processes. The appearance of the sharp zero eKE feature is typical of that expected for thermionic emission [34][35][36] and suggests that the 2 A u can undergo internal conversion to generate vibrationally hot ground state pBQ• -.…”

Section: Electronic Structure and Dynamicsmentioning

confidence: 99%

Ultrafast above-threshold dynamics of the radical anion of a prototypical quinone electron-acceptor

et al. 2013

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. (2013) 'Ultrafast above-threshold dynamics of the radical anion of a prototypical quinone electron-acceptor.', Nature chemistry., 5 (8). pp. 711-717. Further information on publisher's website:https://doi.org/10.1038/nchem.1705Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Quinones are found throughout nature as key electron acceptor intermediates, 1,2 with examples including plastoquinone which is involved in the electron transfer chain of photosystem II, and ubiquinone (coenzyme Q10) which plays a key role in aerobic cellular respiration. 3 The central moiety responsible for the electron accepting ability in quinones is para-benzoquinone (pBQ), shown in Figure 1c. Electron transfer reactions involving pBQ can be highly exergonic and are therefore often classed as being in the Marcus inverted region. [4][5][6][7][8][9][10] This is shown schematically by the green path in Figure 1a, where a barrier between the Gibbs free energy of the reactants and products lowers the rates of the electron transfer process. However, even in the earliest experimental verifications of the inverted region for intramolecular electron transfer, several electron acceptors based on pBQ showed marked deviations from the expected behaviour, with transfer rates approaching those of a barrierless reaction. 11 It has been proposed that such deviations may involve electronically excited states of the product radical anion of para-benzoquinone (pBQ• -), 12 which could provide reaction pathways that bypass the barrier, as shown in Figure 1a with purple arrows. Figure 1b shows the location of these resonances.From the point of view of an electron approaching pBQ, these anionic resonances in the detachment continuum can capture an electron. Subsequent formation of the anionic ground state through internal conversion would redistribute the excess internal energy amongst all the vibrational modes. In a condensed-phase environment, this energy will be quenched by the surroundings. However, the initially formed excited states of pBQ• -can be unbound with respect to electron loss. For the above picture to be feasible, internal conversion must be able to compete with autodetachment. Electron attachment spectra suggest that it can, 26-28 but how does this occur given that these resonances are in some cases > 1 eV above the detachment threshold?In order to gain a fundamental understanding of the processes involved following electron capture, it is necessary to observe the relaxation dynamics in real t...

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“…Negative atomic ions remain an interesting and challenging problem to both experimental and theoretical studies [1][2][3][4]. In the theoretical models we are faced with strong correlation contributions, since these system are far from dominated by a central, nuclear potential, but are rather defined by electron-electron interactions [5].…”

Section: Introductionmentioning

confidence: 99%

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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Structure and dynamics of negative ions

Cited by 115 publications

References 236 publications

Anion Resonances of para-Benzoquinone Probed by Frequency-Resolved Photoelectron Imaging

Anion Resonances of para-Benzoquinone Probed by Frequency-Resolved Photoelectron Imaging

Ultrafast above-threshold dynamics of the radical anion of a prototypical quinone electron-acceptor

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

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