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- Neppl, Stefan, et al.
(författare)
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Probing charge dynamics in bare and dye-sensitized ZnO nanocrystals with time-resolved XPS
- 2016
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Ingår i: International Conference on Ultrafast Phenomena, UP 2016. - 9781943580187 ; Part F20-UP 2016
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Konferensbidrag (refereegranskat)abstract
- Time-resolved XPS is used to monitor charge carrier dynamics in bare and dyesensitized ZnO nanoparticle films upon sub-bandgap excitation. Results are discussed in the context of impurity-related bandgap states and electron transfer from the chromophore.
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- Roth, Friedrich, et al.
(författare)
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Efficient charge generation from triplet excitons in metal-organic heterojunctions
- 2019
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Ingår i: Physical Review B. - 2469-9950. ; 99:2
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Tidskriftsartikel (refereegranskat)abstract
- The success of many emerging molecular electronics concepts hinges on an atomistic understanding of the underlying electronic dynamics. We employ picosecond time-resolved x-ray photoemission spectroscopy (tr-XPS) to elucidate the roles of singlet and triplet excitons for photoinduced charge generation at a copper-phthalocyanine-C60 heterojunction. Contrary to common belief, fast intersystem crossing to triplet excitons after photoexcitation is not a loss channel but contributes to a significantly larger extent to the time-integrated interfacial charge generation than the initially excited singlet excitons. The tr-XPS data provide direct access to the diffusivity of the triplet excitons DCuPc=(1.8±1.2)×10-5cm2/s (where CuPc is copper-phthalocyanine) and their diffusion length Ldiff=(8±3)nm.
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4. |
- Schnorr, Kirsten, et al.
(författare)
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Tracing the 267 nm-Induced Radical Formation in Dimethyl Disulfide Using Time-Resolved X-ray Absorption Spectroscopy
- 2019
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185 .- 1948-7185. ; 10:6, s. 1382-1387
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Tidskriftsartikel (refereegranskat)abstract
- Disulfide bonds are pivotal for the structure, function, and stability of proteins, and understanding ultraviolet (UV)-induced S–S bond cleavage is highly relevant for elucidating the fundamental mechanisms underlying protein photochemistry. Here, the near-UV photodecomposition mechanisms in gas-phase dimethyl disulfide, a prototype system with a S–S bond, are probed by ultrafast transient X-ray absorption spectroscopy. The evolving electronic structure during and after the dissociation is simultaneously monitored at the sulfur L1,2,3-edges and the carbon K-edge with 100 fs (FWHM) temporal resolution using the broadband soft X-ray spectrum from a femtosecond high-order harmonics light source. Dissociation products are identified with the help of ADC and RASPT2 electronic-structure calculations. Rapid dissociation into two CH3S radicals within 120 ± 30 fs is identified as the major relaxation pathway after excitation with 267 nm radiation. Additionally, a 30 ± 10% contribution from asymmetric CH3S2 + CH3 dissociation is indicated by the appearance of CH3 radicals, which is, however, at least partly the result of multiphoton excitation.
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