Angular-resolved Photoelectron Spectroscopy of Superatom Orbitals of Fullerenes

Johansson, J. Olof; Henderson, Gordon G.; Remacle, Françoise; Campbell, Eleanor E. B.

doi:10.1103/physrevlett.108.173401

Cited by 44 publications

(74 citation statements)

References 18 publications

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“…[26,27,28]. Similar calculations have also been performed by employing Linearized Time-Dependent DFT (L-TDDFT), in which free plane waves for the outgoing wave functions are considered in the calculation of the anisotropy parameter β 2 , for various laser frequencies [23]. However, free plane waves might constitute an oversimplication which can significantly impact β 2 , see discussion in Section 5.3.2 and [29].…”

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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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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“…Fullerenes are nanometer-size systems with interesting physical properties, including high polarizability [32], superatomic molecular orbitals [33,34] with macroatom behavior [35], large photoionization cross sections [36,37], and efficient high-harmonic generation [38][39][40]. The ionization and fragmentation of C 60 have been investigated extensively in the past (see, e.g., [35,[41][42][43][44][45][46][47]).…”

mentioning

confidence: 99%

Coherent Electronic Wave Packet Motion inC60Controlled by the Waveform and Polarization of Few-Cycle Laser Fields

Mignolet

Wachter

et al. 2015

Phys. Rev. Lett.

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Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C 60 fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization. DOI: 10.1103/PhysRevLett.114.123004 PACS numbers: 33.80.Eh, 31.15.xv, 42.50.Hz, 71.20.Tx Electrons determine the forces on the nuclei in molecules. Tuning the nonequilibrium electronic dynamics before the onset of significant nuclear motion opens new routes for tailoring chemical reactivity. For few-cycle optical pulses, varying the phase between the envelope and the field amplitude [carrier-envelope phase (CEP)] can be used to control electronic dynamics induced in molecules during the interaction with the pulse [1][2][3]. Electronic dynamics are typically probed indirectly by recording molecular fragmentation patterns of dissociative (ionization) channels exploiting the coupling between the electronic and nuclear degrees of freedom . The analysis of the fragmentation patterns is usually complex-even for simple diatomic molecules-and quickly becomes prohibitively complicated for large polyatomic molecules because of the large number of fragmentation channels [3]. Angularly resolved photoionization by ultrashort laser pulses has been advocated for probing the electronic dynamics before the onset of significant nuclear motion (see, e.g., [27][28][29][30][31] [36,37], and efficient high-harmonic generation [38][39][40]. The ionization and fragmentation of C 60 have been investigated extensively in the past (see, e.g., [35,[41][42][43][44][45][46][47]). C 60 is very stable and is one of the few molecular systems for which the ionization energy is smaller than the lowest fragmentation threshold. Therefore it is an ideal system for probing electronic dynamics, and, when suitably excited, the electronic density oscillates on a nanometer scale. Moreover, in the experiments reported here, the pulse duration is short enough to avoid significant thermionic emission that occurs for longer pulse durations of hundreds of femtoseconds to nanoseconds [48,49]. In this Letter, we demonstrate the control over transient electronic dynamics in a large polyatomic system, the C 60 fullerene, and we find that the angular distribution of direct photoelectrons reflects the spatial localization of the electronic wave packet at about the time of ionization.The electron emission from C 60 as a function of the CEP is recorded with phase-tagged velocity-map imaging (VMI) [50]. Details of the experimental setup are contained in the Supplemental Material [51]. The few-cycle laser pulses are focused into the VM...

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“…The details of the experimental techniques have been provided in previous publications [5,8,9] and will be only briefly described here. The original studies that reported the excitation and subsequent single-photon ionization of Rydberg states in C 60 were carried out with a combined linear time-of-flight photoelectron spectrometer and a time-of-flight mass spectrometer (MS) [5,10].…”

Section: Methodsmentioning

confidence: 99%

“…The emphasis was placed on the determination of the binding energies of the higher lying members of the Rydberg series that were well resolved using 800 nm laser pulses with 1.5 ps duration. In more recent studies, the time-of-flight photoelectron spectrometer was replaced by a velocity map imaging (VMI) spectrometer, illustrated in figure 2 [8,9]. This incorporates a position-sensitive detector consisting of a set of multichannel plates followed by a phosphor screen.…”

Section: Methodsmentioning

confidence: 99%

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Super-atom molecular orbital excited states of fullerenes

Johansson

Bohl

Campbell

2016

Phil. Trans. R. Soc. A.

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Super-atom molecular orbitals are orbitals that form diffuse hydrogenic excited electronic states of fullerenes with their electron density centred at the centre of the hollow carbon cage and a significant electron density inside the cage. This is a consequence of the high symmetry and hollow structure of the molecules and distinguishes them from typical low-lying molecular Rydberg states. This review summarizes the current experimental and theoretical studies related to these exotic excited electronic states with emphasis on femtosecond photoelectron spectroscopy experiments on gas-phase fullerenes. This article is part of the themed issue ‘Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene’.

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Angular-resolved Photoelectron Spectroscopy of Superatom Orbitals of Fullerenes

Cited by 44 publications

References 18 publications

On the dynamics of photo-electrons in C₆₀

On the dynamics of photo-electrons in C₆₀

Coherent Electronic Wave Packet Motion inC60Controlled by the Waveform and Polarization of Few-Cycle Laser Fields

Super-atom molecular orbital excited states of fullerenes

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Angular-resolved Photoelectron Spectroscopy of Superatom Orbitals of Fullerenes

Cited by 44 publications

References 18 publications

On the dynamics of photo-electrons in C60

On the dynamics of photo-electrons in C60

Coherent Electronic Wave Packet Motion inC60Controlled by the Waveform and Polarization of Few-Cycle Laser Fields

Super-atom molecular orbital excited states of fullerenes

Contact Info

Product

Resources

About

On the dynamics of photo-electrons in C₆₀

On the dynamics of photo-electrons in C₆₀