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Photoexcitation

About: Photoexcitation is a research topic. Over the lifetime, 5874 publications have been published within this topic receiving 134733 citations.


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Journal ArticleDOI
Oriol Vendrell1
15 Jun 2018
TL;DR: In this article, the photochemistry of a molecular ensemble coupled to a resonance cavity and triggered by a femtosecond laser pulse is investigated from a real-time, quantum dynamics perspective with the multi-configuration time-dependent Hartree method.
Abstract: The photochemistry of a molecular ensemble coupled to a resonance cavity and triggered by a femtosecond laser pulse is investigated from a real-time, quantum dynamics perspective with the multi-configuration time-dependent Hartree method. Coherent excitation of a superposition of electronic states in the ensemble leads to superradiant energy transfer to the cavity characterized by quadratic scaling with the number of molecules. Electronic decoherence associated with loss of nuclear wave packet overlap among those states destroys superradiant energy transfer, returning to a linear regime. For equal pump laser conditions, the photoexcitation probability per molecule decreases with increase of the number of molecules inside the cavity. This is caused by a loss of resonance condition of the laser with the bright electronic-photonic states of the coupled cavity-ensemble system. Increase of the laser bandwidth restores the energy transferred per molecule and the trigger probability remains independent of the number of molecules in the cavity.

82 citations

Journal ArticleDOI
TL;DR: The UV source has been fully characterized spatially, spectrally, and temporally and its potential for time and angle-resolved photoemission is demonstrated through Fermi surface mapping and photoexcited electron dynamics in Bismuth.
Abstract: A novel experimental apparatus for time and angle-resolved photoemission on solid surfaces is presented. A 6.28 eV laser source operating at 250 kHz repetition rate is obtained by frequency mixing in nonlinear beta barium borate crystals. This UV light source has a high photon flux of 1013 photons/s with relatively low number of photons/pulse so that Fermi surface mapping over a wide region of the Brillouin zone is possible while mitigating space charge effects. The UV source has been fully characterized spatially, spectrally, and temporally. Its potential for time and angle-resolved photoemission is demonstrated through Fermi surface mapping and photoexcited electron dynamics in Bismuth. True femtosecond time resolution <65 fs is obtained while the energy resolution of 70 meV appears to be mainly limited by the laser bandwidth.

82 citations

Journal ArticleDOI
TL;DR: In this article, a bacteriochlorin-C60 dyad and a zinc chlorin dyad with the same short spacer have been synthesized and the rate constants for the charge-separation (CS) processes in these dyads were determined by fluorescence lifetime measurements of the dyads.
Abstract: A bacteriochlorin-C60 dyad (H2BCh-C60) and a zinc chlorin dyad (ZnCh-C60) with the same short spacer have been synthesized. The rate constants for the charge-separation (CS) processes in these dyads were determined by fluorescence lifetime measurements of the dyads. The charge-recombination (CR) rate constants of the dyads were determined using laser flash photolysis. The photoexcitation of the zinc chlorin-C60 dyad results in formation of the long-lived radical ion pair, which has absorption maxima at 790 and 1000 nm due to the zinc chlorin radical cation and the C60 radical anion, respectively. Photoexcitation of the free-base bacteriochlorin-C60 dyad with the same short linkage leads to formation of the radical ion pair, which decays quickly to the triplet excited state of the bacteriochlorin moiety. The driving force dependence of the electron-transfer rate constants of these dyads with a short spacer affords a small reorganization energy (λ = 0.51 eV) as compared with the λ value (0.66 eV) of zinc po...

81 citations

Journal ArticleDOI
TL;DR: In this paper, the photoionization of neutral liquid helium droplets was studied using synchrotron radiation at photon energies ranging from 15 to 30 eV, and the mass spectra as well as total and mass selective ion yields were measured as a function of the photon energy for different droplet sizes.
Abstract: The photoionization of neutral liquid helium droplets (mean particle number 〈N〉=102–107) was studied using synchrotron radiation at photon energies ranging from 15 to 30 eV. Mass spectra as well as total and mass selective ion yields were measured as a function of the photon energy for different droplet sizes. The experiments indicate that ionization occurs not only by a direct process at photon energies above the atomic ionization potential but also at energies below the threshold by an autoionization process. The latter ionization mechanism proceeds via the electronically excited states of the neutral droplet, which show a strong neutral droplet size dependence. For large neutral droplets HeN(〈N〉≳104) retarding field measurements established that a predominant part of the total ion yield results from larger cluster ions He+k(k≳103). These measurements also show that a decay by fluorescence emission is much more probable than one by ionization following the photoexcitation process. In droplets with embed...

81 citations

Journal ArticleDOI
TL;DR: In this article, the spectra of luminescence and photoexcitation as well as emission decay kinetics in various parts of spectra are investigated in ZnWO4 and CdWO 4 crystals in a wide temperature range (4.2 to 300 K).
Abstract: The spectra of luminescence and photoexcitation as well as emission decay kinetics in various parts of spectra are investigated in ZnWO4 and CdWO4 crystals in a wide temperature range (4.2 to 300 K). The bands of red afterglow and of rapidly decaying violet luminescence are observed for the first time. The likeness of the emission properties of ZnWO4 and CdWO4 allows the explanation of the luminescence in these tungstenite type crystals in terms of configurational coordinate diagrams of self-activated radiation centre and of self-trapped exciton. [Russian Text Ignored].

81 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023249
2022529
2021221
2020204
2019183
2018256