From Above Threshold Ionization to Statistical Electron Emission: The Laser Pulse-Duration Dependence of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>C</mml:mi></mml:mrow><mml:mrow><mml:mn>60</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Photoelectron Spectra

Campbell, E. E. B.; Hansen, Klavs; Hoffmann, K.; Korn, G.; Tchaplyguine, Maxim; Wittmann, M.; Hertel, IV Iv

doi:10.1103/physrevlett.84.2128

Cited by 151 publications

(112 citation statements)

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“…Faster, subpicosecond processes occur when the energy is partitioned only among electronic states. This result can be realized for states excited by resonant collisional electronic energy transfer (51) or from electronic excitation with short (few to tens of fs) laser pulses (52). Such electronic energy redistribution can be initiated with as pulses.…”

Section: Resultsmentioning

confidence: 99%

An electronic time scale in chemistry

Remacle

Levine

2006

Proc. Natl. Acad. Sci. U.S.A.

385

335

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Ultrafast, subfemtosecond charge migration in small peptides is discussed on the basis of computational studies and compared with the selective bond dissociation after ionization as observed by Schlag and Weinkauf. The reported relaxation could be probed in real time if the removal of an electron could be achieved on the attosecond time scale. Then the mean field seen by an electron would be changing rapidly enough to initiate the migration. Tyrosine-terminated tetrapeptides have a particularly fast charge migration where in <1 fs the charge arrives at the other end. A femtosecond pulse can be used to observe the somewhat slower relaxation induced by correlation between electrons of different spins. A slower relaxation also is indicated when removing a deeper-lying valence electron. When a chromophoric amino acid is at one end of the peptide, the charge can migrate all along the peptide backbone up to the N end, but site-selective ionization is probably easier to detect for tryptophan than for tyrosine.attosecond lasers ͉ charge transfer ͉ protein mass spectrometry A chemical rearrangement occurs when atoms in a molecule change their specific arrangement. The time scale of chemistry is therefore the time scale for the motion of atoms (1, 2). The forces operating on the atoms determine the path of this motion. In the Born-Oppenheimer approximation, it is the averaging over the much faster motion of the electrons that specifies the potential energy and hence the forces. The physical picture for this approximation is that the electrons instantly adjust to the current position of the nuclei so that the equilibrium arrangement of the bonded atoms is determined as a minimum of the electronic energy. In the Born-Oppenheimer approximation, the system is confined to be in a single stationary electronic state, and if this confinement is strict then there is no electronic time scale that is relevant to chemistry. During a chemical rearrangement, the motion of the atoms can be accompanied by a reorganization of the electronic structure, and recent experimental progress allows for probing this change (3) in real time. However, it is the motion of the nuclei that sets the time scale because the electronic reorganization exactly tracks the shifts in the positions of the nuclei. As the heavier nuclei move, the light electrons immediately adapt.It is recognized that the energy of the same stationary electronic state can have two distinct minima, where the electronic charge distribution has a quite different character. At the immediate vicinity of either of the two configurations of the nuclei, the motion is bounded, but larger-amplitude motion can connect the two hollows. Major intramolecular charge reorganization follows upon a change in nuclear geometry (4-8). The time scale of the charge shuffling is that of the motion of the nuclei relocating between the two configurations.Optical excitation can prepare a nonstationary state, and such a state is often known as the optically bright state. The optically bright state is not sta...

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Section: Resultsmentioning

confidence: 99%

An electronic time scale in chemistry

Remacle

Levine

2006

Proc. Natl. Acad. Sci. U.S.A.

385

335

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“…Essentially three different ionization regimes can be distinguished, which depend sensitively on the excitation time scale. 9,21 For very short pulses ͑FWHMϽ 70 fs͒ ͑FWHM denotes full width at half maximum͒ the excitation energy tends to remain mainly in the electronic systems and multiply charged C 60 q+ ions are observed, formed by direct multiphoton ionization ͑MPI͒, possibly enhanced by transient, quasiresonant multiphoton excitation 9 of the plasmon resonance 22 between 10 and 28 eV. Relatively few fullerenelike fragments C 60−2m q+ are generated and detected in typical mass spectra under these conditions.…”

Section: Introductionmentioning

confidence: 99%

“…For longer pulses ͑70 fsϽ Ͻ picoseconds͒ the absorbed energy is efficiently coupled among electronic degrees of freedom, and any fingerprints for a clear SAE ionization mechanism, such as above threshold ionization ͑ATI͒, disappear. 21 For still longer pulses ͑ Ͼ picoseconds͒, electron-electron and electronphonon couplings lead to substantial excess vibrational energy in the system, multiply charged ions disappear from the mass spectra, and massive fragmentation into singly charged fullerenelike species with m Շ 10, as well as into small fragments C k + with k Շ 27, are observed, resulting in the well known bimodal mass distribution. In addition, delayed ionization sets in.…”

Section: Introductionmentioning

confidence: 99%

“…Inelastic electron-electron scattering and electron-phonon coupling are thought to occur on time scales el from some tens to some hundreds of femtoseconds. 21,24 In previous studies such information was extracted rather indirectly from pulse duration dependent experiments. In contrast, femtosecond pump-probe techniques offer a more direct view into the dynamics with a temporal resolution of nuclear motion by comparing the time-dependent signals of parent C 60 q+ and fragment C 60−2m q+ ions ͑transients͒.…”

Section: Introductionmentioning

confidence: 99%

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Ultrafast energy redistribution in C60 fullerenes: A real time study by two-color femtosecond spectroscopy

Shchatsinin

Laarmann

Zhavoronkov

et al. 2008

The Journal of Chemical Physics

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Strong-field excitation and energy redistribution dynamics of C 60 fullerenes are studied by means of time-resolved mass spectrometry in a two-color femtosecond pump-probe setup. Resonant pre-excitation of the electronic system via the first dipole-allowed HOMO→ LUMO+ 1͑t 1g ͒ ͑HOMO denotes highest occupied molecular orbital and LUMO denotes lowest unoccupied molecular orbital͒ transition with ultrashort 25 fs pulses at 399 nm of some 10 12 W cm −2 results in a highly nonequilibrium distribution of excited electrons and vibrational modes in the neutral species. The subsequent coupling among the electronic and nuclear degrees of freedom is monitored by probing the system with time-delayed 27 fs pulses at 797 nm of some 10 13 W cm −2 . Direct information on the characteristic relaxation time is derived from the analysis of transient singly and multiply charged parent and fragment ion signals as a function of pump-probe delay and laser pulse intensity. The observed relaxation times el Ӎ 60-400 fs are attributed to different microcanonical ensembles prepared in the pre-excitation process and correspond to different total energy contents and energy sharing between electronic and vibrational degrees. The characteristic differences and trends allow one to extract a consistent picture for the formation dynamics of ions in different charge states and their fullerenelike fragments and give evidence to collective effects in multiple ionization such as plasmon-enhanced energy deposition.

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“…Experimentally, thanks to the recent development of ultrafast spectroscopy techniques, it is now possible to monitor the femtosecond dynamics of an electron gas confined in metallic nanostructures such as thin films [1,2,3,4,5,6,7,8], nanotubes [9], metal clusters [10,11] and nanoparticles [6,7,12,13]. Therefore, meaningful comparisons between experimental measurements and numerical simulations based on microscopic theories are becoming possible.…”

Section: Introductionmentioning

confidence: 99%