Thermal electron emission from the hot electronic subsystem of vibrationally cold C60

Hansen, Klavs; Hoffmann, K.; Campbell, Eleanor E. B.

doi:10.1063/1.1584671

Cited by 69 publications

(101 citation statements)

References 26 publications

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“…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• -. This can subsequently loose an electron in a statistical fashion.…”

Section: Electronic Structure and Dynamicsmentioning

confidence: 79%

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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Section: Electronic Structure and Dynamicsmentioning

confidence: 79%

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

et al. 2013

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“…The density of states of graphite for threshold photoemission is flat [53] and therefore not a factor in our analysis. Similar assumptions of thermal equilibrium for the electronic system were made to analyze the ultrafast multiphoton excitation of blackbody luminescence from graphene, thermionic electron emission from carbon nanotube forests, and electron or ion emission from C 60 [14,15,28,86,87]. Indeed, fitting representative s-polarized mPP spectra for hν ¼ 1.…”

Section: Resultsmentioning

confidence: 99%

Ultrafast Multiphoton Thermionic Photoemission from Graphite

et al. 2017

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Electronic heating of cold crystal lattices in nonlinear multiphoton excitation can transiently alter their physical and chemical properties. In metals where free electron densities are high and the relative fraction of photoexcited hot electrons is low, the effects are small, but in semimetals, where the free electron densities are low and the photoexcited densities can overwhelm them, the intense femtosecond laser excitation can induce profound changes. In semimetal graphite and its derivatives, strong optical absorption, weak screening of the Coulomb potential, and high cohesive energy enable extreme hot electron generation and thermalization to be realized under femtosecond laser excitation. We investigate the nonlinear interactions within a hot electron gas in graphite through multiphoton-induced thermionic emission. Unlike the conventional photoelectric effect, within about 25 fs, the memory of the excitation process, where resonant dipole transitions absorb up to eight quanta of light, is erased to produce statistical Boltzmann electron distributions with temperatures exceeding 5000 K; this ultrafast electronic heating causes thermionic emission to occur from the interlayer band of graphite. The nearly instantaneous thermalization of the photoexcited carriers through Coulomb scattering to extreme electronic temperatures characterized by separate electron and hole chemical potentials can enhance hot electron surface femtochemistry, photovoltaic energy conversion, and incandescence, and drive graphite-to-diamond electronic phase transition.

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“…Thermal effects are so far mainly described phenomenologically, see e.g. [19]. A detailed account of collisional thermalization is presently only possible in semi-classical models of clusters dynamics [48,49], which, however, work so far only in metal clusters.…”

Section: On the Formalismmentioning

confidence: 99%

“…More recently, a great manifold of precision measurements of PES and/or PAD have been performed, exploring several dynamical ranges, see e.g. [9,18,19,20,21,22,23].…”

Section: Introductionmentioning

confidence: 99%

On the dynamics of photo-electrons in C₆₀

Gao¹,

Wopperer²,

Dinh³

et al. 2015

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

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Abstract. We explore photo-electron spectra (PES) and photo-electron angular distributions (PAD) of C 60 with time-dependent density functional theory (TDDFT) in real time. To simulate experiments in gas phase, we consider isotropic ensembles of cluster orientations and perform orientation averaging of the TDDFT calculations. First, we investigate ionization properties of C 60 by one-photon processes in the range of VUV energies. The PES map the energies of the occupied single-particle states, while the weights of the peaks in PES are given by the depletion of the corresponding level. The different influences can be disentangled by looking at PES from slightly different photon frequencies. PAD in the one-photon regime can be characterized by one parameter, the anisotropy. This single parameter unfolds worthwhile information when investigating the frequency and state dependences. We also discuss the case of multi-photon ionization induced by strong infrared laser pulses in C 60 . In agreement with measurements, we find that the PES show a regular comb of peaks separated by the photon energy. Our calculations reveal that this happens because only very few occupied states of C 60 near the ionization threshold contribute to emission and that these few states happen to cooperate filling the same peaks. The PAD show a steady increase of anisotropy with increasing photon order.

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Thermal electron emission from the hot electronic subsystem of vibrationally cold C60

Cited by 69 publications

References 26 publications

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

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

Ultrafast Multiphoton Thermionic Photoemission from Graphite

On the dynamics of photo-electrons in C₆₀

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Thermal electron emission from the hot electronic subsystem of vibrationally cold C60

Cited by 69 publications

References 26 publications

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

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

Ultrafast Multiphoton Thermionic Photoemission from Graphite

On the dynamics of photo-electrons in C60

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On the dynamics of photo-electrons in C₆₀