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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: A simple method to induce optical activity in the terahertz (THz) region using photoexcited carriers in a semiconductor substrate with metal two-dimensional chiral masks is proposed and demonstrated.
Abstract: We propose and demonstrate a simple method to induce optical activity in the terahertz (THz) region using photoexcited carriers in a semiconductor substrate with metal two-dimensional chiral masks, which does not show optical activity without photoexcitation. The three-dimensional chirality induced by the combination of photocarriers and metal mask gives rise to the optical activity. With this simple method, we can develop THz polarization modulation techniques applicable for biology, chemistry, and material sciences.
55 citations
TL;DR: In this article, the authors used the Livermore X-ray Spectral Synthesizer to calculate spectral models of highly charged ions based on HULLAC atomic data and showed that the Chandra HETG spectrum of the intermediate polar EX Hydrae is significantly smaller than that observed in the Sun or other late-type stars.
Abstract: We show that the Fe XVII I(17.10 u/I(17.05 u line ratio observed in the Chandra HETG spectrum of the intermediate polar EX Hydrae is significantly smaller than that observed in the Sun or other late-type stars. Using the Livermore X-ray Spectral Synthesizer, which calculates spectral models of highly charged ions based on HULLAC atomic data, we find that the observed I(17.10 u/I(17.05 u line ratio can be explained if the plasma density ne > 3 × 10 14 cm −3 . However, if photoexcitation is included in the level population kinetics, the line ratio can be explained for any density if the photoexcitation temperature Tbb > 55 kK. For photoexcitation to dominate the Fe XVII level population kinetics, the relative size of the hotspot on the white dwarf surface must be f 2 × 10 14 cm −3 for the post-shock flow. Either way, then, the Chandra HETG spectrum of EX Hya requires a plasma density which is orders of magnitude greater than that observed in the Sun or other late-type stars.
55 citations
TL;DR: In this article, the authors investigated the UV-induced desorption of O2 from a reduced TiO2 rutile surface using a cluster model, where the low-lying excited electronic states of the adsorbate-surface system and the transition dipole moments were calculated with a cluster approach.
Abstract: We investigate the UV-induced desorption of O2 from a reduced TiO2 rutile surface. The desorption mechanism considered is a direct, optical excitation of the adsorbate-substrate complex. The low-lying excited electronic states of the adsorbate-surface system and the transition dipole moments are calculated with a cluster model. We also estimate the effects of nonadiabatic coupling on the desorption yield. As a consequence of the localized nature of the adsorption process, ground state properties calculated with the cluster model agree well with previous results obtained with a slab model. To reduce the size of the calculation, we use optimal orbitals for each of the interacting electronic states, followed by transformation to biorthonormal orbital sets. Comparison with experimental photodesorption cross-section data shows excellent agreement for photon energies close to the vertical transition energy. At higher energies, we speculate that substrate-mediated electronic excitation mechanisms must be include...
55 citations
TL;DR: An ultrafast optical response is studied in a quasi-one-dimensional halogen-bridged mixed-valence metal complex [Pt(en)2I2] (ClO4)(4) with ultrafast time resolution with oscillatory modulations in the time-resolved reflectivity.
Abstract: An ultrafast optical response is studied in a quasi-one-dimensional halogen-bridged mixed-valence metal complex [Pt(en)(2)] [Pt(en)2I2] (ClO4)(4) with ultrafast time resolution. Wave packet motions both in the ground and self-trapped exciton (STE) states are observed as oscillatory modulations in the time-resolved reflectivity. The wave packet motion on the STE potential surface begins after about 50 fs with respect to the photoexcitation. This delay is attributed to the lattice relaxation from the free exciton state to the STE state.
55 citations
TL;DR: In this article, a type-II heterostructured CdTe/CdSe core/shell nanocrystals (quantum dots, QDs) are explored as sensitizers in a QD-sensitized photoelectrochemical solar cell.
Abstract: Type-II heterostructure CdTe/CdSe core/shell nanocrystals (quantum dots, QDs) are explored as sensitizers in a QD-sensitized photoelectrochemical solar cell. These QDs comprise a hole-localizing core and an electron-localizing shell. Among their advantages is the significant red shift of the absorption edge of the heterostructured QD relative to its two constituents due to spatially indirect absorption leading to improved absorption characteristics, intraparticle exciton dissociation upon photoexcitation, and a relatively small content of the less abundant tellurium element. Upon incorporation in a sensitized solar cell utilizing a porous TiO2 and a polysulfide electrolyte, these QDs exhibited efficient charge separation and high internal quantum efficiency despite hole localization in the CdTe core. Monochromatic incident photon-to-current conversion efficiency (IPCE) measurement shows a spectrally broad photoresponse spanning the whole visible spectrum and reaching up to ∼900 nm.
55 citations