Ultrafast internal conversion and photodissociation of molecules excited by femtosecond 155 nm laser pulses

Farmanara, P.; Steinkellner, Oliver; Wick, Markus; Wittmann, M.; Korn, G.; Stert, V.; Radloff, W.

doi:10.1063/1.479932

Cited by 77 publications

(87 citation statements)

References 20 publications

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“…In particular, this ion state was also involved in the experiments with UV probing (ref. [7,8] This work also demonstrates that it is possible -and makes sense -to distinguish different phases during dissociation, during which different processes and/or features of the potentials can be observed. To some extent this may be surprising for a molecule with only two atoms and just one potential involved in the excited neutral molecule.…”

Section: Further Remarks On the Atomic Ion Signal And Its Interpretationmentioning

confidence: 92%

“…We report on time-resolved photodissociation in the continuum with much better resolution than before. In previous such investigations, Farmanara et al used pulses at 155 nm (duration 350 -450 fs) to excite the oxygen, probing it by ionization at 258 nm [7]; they reported a decay time of the O 2 + signal of 40 fs, obtained by deconvolution.…”

Section: Confidential: Not For Distribution Submitted To Iop Publishmentioning

confidence: 99%

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Time-resolved photodissociation of oxygen at 162 nm

Trushin¹,

Schmid²,

Fuß³

2011

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

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Oxygen was excited by 10-fs pulses in the Schumann-Runge continuum at 162 nm, which is by 0.57 eV above the dissociation limit. It was probed by high-intensity ionization at 810 nm with 10 14 W cm −2 , measuring the ion yields. The O 2 + signal decays in 4.3 fs, which is much shorter than the expected time for dissociation. It is ascribed to a rapid decay of the ionization probability. In a similar time, the ion in the second excited state (with excess energy taken over from the neutral) reaches the dissociation limit, whereas this time would be much longer from the two lower ion states. In fact, the O + signal rises to a (first) maximum at 6 fs. The preference for the higher ion state is rationalized by an intermediate resonance in the neutral molecule, for which the polarization dependence also provides evidence. But the shape of the O + signal is very odd: it exhibits three maxima (at 6, 29 and 53 fs) of increasing intensity, before decaying rapidly (≤3.5 fs) to a pedestal. In contrast to the first maximum, the others appear at times when there is practically no interatomic force left in the excited state. We postulate a highly repulsive doubly excited state as a resonance for interpreting the second maximum, and for the third an ion-pair state lying further outside. Comparison is made with enhanced ionization, which has often been found at large interatomic distances on multiple ionization in strong laser fields. Consistent with this mechanism is the absence of similar observations at negative delay times, where five fundamental photons act as a pump and the fifth harmonic as a probe.

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Section: Further Remarks On the Atomic Ion Signal And Its Interpretationmentioning

confidence: 92%

Section: Confidential: Not For Distribution Submitted To Iop Publishmentioning

confidence: 99%

Time-resolved photodissociation of oxygen at 162 nm

Trushin¹,

Schmid²,

Fuß³

2011

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

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“…Early experimental attempts in our group to follow this dynamics directly, using 350 fs pulses at 155 nm, were only able to establish an upper bound of ≤ 20 fs for the excited state "lifetime." 15 12 from a pump-probe experiment by exciting water molecules in a cell, using 12 fs pulses of a few nJ at 162 nm. Electronic absorption spectra have been modeled with state of the art quantum theory by analyzing the wave packet motion on the excited state potential energy surface (PES)-leading to a wealth of data on H 2 O and more recently also on clusters, 4,[16][17][18][19] in particular on the water dimer 7,10,11,20 where the excitedÃ state is characterized by a π D σ * A electron configuration referring to the donor (D) and acceptor (A) oxygen electron.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast photo-excitation dynamics in isolated, neutral water clusters

Liu

Müller

Beutler

et al. 2011

The Journal of Chemical Physics

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Using the efficient nonlinear conversion scheme which was recently developed in our group [M. Beutler, M. Ghotbi, F. Noack, and I. V. Hertel, Opt. Lett. 134, 1491 (2010); M. Ghotbi, M. Beutler, and F. Noack, ibid 35, 3492 (2010)] to provide intense sub-50 fs vacuum ultraviolet laser pulses we have performed the first real time study of ultrafast, photo-induced dynamics in the electronically excited Ã-state of water clusters (H(2)O)(n) and (D(2)O)(n) , n=2-10. Three relevant time scales, 1.8-2.5, 10-30, and 50-150 fs, can be distinguished which-guided by the available theoretical results-are attributed to H (D)-ejection, OH (OD) dissociation, and a nonadiabatic transition through a conical intersection, respectively. While a direct quantitative comparison is only very preliminary, the present results provide a crucial test for future modeling of excited state dynamics in water clusters, and should help to unravel some of the many still unresolved puzzles about water.

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“…The lifetime of benzene excited at 155 nm was also measured to be about 50 fs but in this case the decay is from the Rydberg states. 13 Thus, we conclude that the H atom is produced from the ground state after internal conversions from the initially excited Rydberg states by a nanosecond pulse of two photon absorption at 243.2 nm. The available energy that can be distributed among products is thus 519.6 kJ/mol, from which the fraction into product translation is 0.13.…”

Section: Discussionmentioning

confidence: 99%

Two Photon Dissociation of Benzene, Phenylacetylene, and Benzaldehyde at 243 nm: Translational Energy Releases in the H Atom Channel

2002

Bulletin of the Korean Chemical Society

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Hydrogen atom production channels from photodissociation of benzene, phenylacetylene, and benzaldehyde at 243 nm have been investigated by detecting H atoms using two photon absorption at 243.2 nm and induced fluorescence at 121.6 nm. Translational energies of the H atoms were measured by Doppler broadened H atom spectra. By absorption of two photons at 243 nm, the H atoms are statistically produced from benzene and phenylacetylene whereas the H atoms from the aldehyde group in benzaldehyde are produced from different pathways. The possible dissociation mechanisms are discussed from the measured translational energy releases.

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Ultrafast internal conversion and photodissociation of molecules excited by femtosecond 155 nm laser pulses

Cited by 77 publications

References 20 publications

Time-resolved photodissociation of oxygen at 162 nm

Time-resolved photodissociation of oxygen at 162 nm

Ultrafast photo-excitation dynamics in isolated, neutral water clusters

Two Photon Dissociation of Benzene, Phenylacetylene, and Benzaldehyde at 243 nm: Translational Energy Releases in the H Atom Channel

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