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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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TL;DR: The results demonstrate the potential of both time-domain spectroscopic techniques to resolve photochemical dynamics, including fingerprint frequencies which directly reflect changes in bonding and structure in the nascent sample.
Abstract: Pump-impulsive vibrational spectroscopy (pump-IVS) is used to record excited state vibrational dynamics following photoexcitation of two carotenoids, β-carotene and lycopene, with <30 fs temporal resolution, and covering the full vibrational spectrum of the investigated chromophores. The results record the course of S2–S1 internal conversion, followed by vibrational relaxation and decay to the electronic ground state. This interpretation is corroborated by comparison with pump-degenerate-four-wave-mixing (pump-DFWM) experiments on the same systems. The results demonstrate the potential of both time-domain spectroscopic techniques to resolve photochemical dynamics, including fingerprint frequencies which directly reflect changes in bonding and structure in the nascent sample. The exclusive strengths and limitations of these two methods are compared with those presented by the frequency-domain Femtosecond Stimulated Raman Scattering (FSRS) technique, highlighting the complementary nature of the three, and the benefits of using them in concert to investigate vibrational dynamics in reactive species.

61 citations

Journal ArticleDOI
TL;DR: In this paper, a time resolved core level spectroscopy study was performed on photoexcited Si(111)2×1 surfaces with subnanosecond resolution, which enabled measuring band bending fluctuations, caused by surface carrier dynamics, during the first nanosecond after photoexcitation; differences in the Si2p core level lineshape, dependent on the pumpprobe time delay, were also observed.
Abstract: Combining the use of a UV storage ring free electron laser and of synchrotron radiation, a time resolved core level spectroscopy study has been performed on photoexcited Si(111)2×1 surfaces with subnanosecond resolution. This enabled us to measure band bending fluctuations, caused by surface carrier dynamics, during the first nanosecond after photoexcitation; differences in the Si2p core level lineshape, dependent on the pump-probe time delay, were also observed. The presence of defects was found to reduce the fluctuations and make the carrier recombination process faster.

61 citations

Journal ArticleDOI
TL;DR: In this paper, the photodissociation of Mo(CO)6 adsorbed on potassium free and potassiumpreadsorbed Cu(111) and Si(111)-7×7 at 85 K has been studied under ultrahigh vacuum conditions.
Abstract: Photodissociation of Mo(CO)6 adsorbed on potassium‐free and potassium‐preadsorbed Cu(111) and Si(111)7×7 at 85 K has been studied under ultrahigh vacuum conditions. The photodissociation yield has been measured as a function of photon power (0.5–30 mW/cm2 ), wavelength (250–800 nm), polarization (s and p), and incident angle (20°–70°). Two surface photoreaction mechanisms are considered: (i) direct electronic excitation of the adsorbate and (ii) attachment of photogenerated hot carriers to the adsorbate. The photodissociation spectra obtained on K‐free Cu(111) and Si(111)7×7 exhibit the same resonant structure as the absorption spectrum of Mo(CO)6. Photodissociation of Mo(CO)6 on K‐free surfaces is thus determined to be dominated by direct electronic excitation of the adsorbate, which proceeds via a single‐photon process. A new photodissociation channel is opened on K‐preadsorbed surfaces. The photoyield increases substantially in the UV and extends to the visible and near IR. By studying the wavelength a...

61 citations

Journal ArticleDOI
TL;DR: These results are compared with multiscale Born-Oppenheimer molecular dynamics simulations and demonstrate how off-resonance excitation can be used to prepare a vibrationally cold excited-state population complemented by a structure-dependent depletion of the ground- state population which subsequently evolves in time, allowing direct tracking of ground-state structural dynamics.
Abstract: We report x-ray free electron laser experiments addressing ground-state structural dynamics of the diplatinum anion Pt2POP4 following photoexcitation. The structural dynamics are tracked with <100 fs time resolution by x-ray scattering, utilizing the anisotropic component to suppress contributions from the bulk solvent. The x-ray data exhibit a strong oscillatory component with period 0.28 ps and decay time 2.2 ps, and structural analysis of the difference signal directly shows this as arising from ground-state dynamics along the PtPt coordinate. These results are compared with multiscale Born-Oppenheimer molecular dynamics simulations and demonstrate how off-resonance excitation can be used to prepare a vibrationally cold excited-state population complemented by a structure-dependent depletion of the ground-state population which subsequently evolves in time, allowing direct tracking of ground-state structural dynamics. (Less)

61 citations

Journal ArticleDOI
TL;DR: It is demonstrated that the long-lived photocarriers associated with the peaks at 0.81 eV and below are charged bipolarons, and the 0.96- and 1.04-eV bands are tentatively assigned to vibronic excitations of the bipolarons.
Abstract: Photoinduced absorption is observed for the polydicarbazolyldiacetylene in the microcrystalline state. The absorption spectrum shows well-defined excitonic features, very similar to those observed for the same polymer in the single-crystal form. Photoexcitation at 2.54 eV gives rise to a structured luminescence emission with the maximum around 1.7 eV. The photoinduced absorption spectrum shows three well-resolved peaks at 0.81, 0.96, and 1.26 eV, a shoulder at 1.04 eV, and a band with a maximum below 0.3 eV. By analyzing the dependence of the photoinduced signals on temperature, laser intensity, phase detection, and chopper frequency, we demonstrate that the long-lived photocarriers associated with the peaks at 0.81 eV and below 0.3 eV are charged bipolarons. The 0.96- and 1.04-eV bands are tentatively assigned to vibronic excitations of the bipolarons. Moreover, the 1.26-eV band has been assigned here to a triplet exciton transition. The existence of a correlation between the type of long-lived photogenerated defects and the polymer disorder is also discussed.

61 citations


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