Topic
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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16 Apr 2012
TL;DR: In this article, the two-level system was used for charge transfer and transport and other modulation techniques in the two level system, including charge transfer, pump-probe and other modulation techniques.
Abstract: 1 Introduction 2 Radiation-Matter-Interaction in the Two-Level-System 3 Molecular Exciton 4 Excited States in Solids 5 Photoexcitation Dynamics 6 Photphysics Tool Box 7 Vibrational Spectroscopy 8 Charge Transfer and Transport 9 Pump-probe and Other Modulation Techniques 10 Conclusions and Future Perspectives
77 citations
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TL;DR: Exitonic Rydberg states with distinct formation pathways are revealed by observing the multiple resonant, internal quantum transitions using ultrafast terahertz quasi-particle transport in the hybrid perovskite system.
Abstract: How photoexcitations evolve into Coulomb-bound electron and hole pairs, called excitons, and unbound charge carriers is a key cross-cutting issue in photovoltaics and optoelectronics Until now, the initial quantum dynamics following photoexcitation remains elusive in the hybrid perovskite system Here we reveal excitonic Rydberg states with distinct formation pathways by observing the multiple resonant, internal quantum transitions using ultrafast terahertz quasi-particle transport Nonequilibrium emergent states evolve with a complex co-existence of excitons, carriers and phonons, where a delayed buildup of excitons under on- and off-resonant pumping conditions allows us to distinguish between the loss of electronic coherence and hot state cooling processes The nearly ∼1 ps dephasing time, efficient electron scattering with discrete terahertz phonons and intermediate binding energy of ∼135 meV in perovskites are distinct from conventional photovoltaic semiconductors In addition to providing implications for coherent energy conversion, these are potentially relevant to the development of light-harvesting and electron-transport devices The generation of bound electron and hole pairs—excitons—is a key process in photovoltaic technologies, yet it is challenging to follow their initial dynamics Here, Luoet al probe the Rydberg eigenstates that characterize the excitonic transport and coherent conversion in a perovskite material
77 citations
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TL;DR: The finding that the heat capacity of gold nanoparticles can be changed upon UV laser excitation is important for understanding the fundamental nature of noble metal nanoparticles.
Abstract: An in situ spectroscopic study of the nanosecond laser-induced melting and size reduction of pseudospherical gold nanoparticles with 54 ± 7 nm diameter allowed the observation of a heating efficiency that was very dependent on the excitation wavelength. A remarkably greater efficiency was observed for the photothermal effect of interband excitation than that of intraband excitation. This noteworthy observation is ascribed to an altered electron heat capacity, ce, during photoexcitation depending on the excitation energy, which is a phenomenon that has not been realized previously. As a result, a 60% reduction of the specific heat capacity, cp, compared to that of bulk gold was obtained for interband excitation at 266 nm whereas the cp value for the excitation of the intraband transition at 532 nm was unaltered. A semiquantitative explanation was given for this striking phenomenon induced by interband excitation in which excitation−relaxation cycles of electrons upon excitation of 5d electrons to the 6sp b...
77 citations
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TL;DR: In this paper, the authors obtained the photoabsorption and fluorescence cross sections of C2H2, and the quantum yield for producing the C 2H-asterisk fluorescence from photodissociation was measured in the 106-136.5 nm region.
Abstract: Synchrotron radiation light source measurements were conducted in the 105-155 nm region to obtain the photoabsorption and fluorescence cross sections of C2H2, and the quantum yield for producing the C2H-asterisk fluorescence from C2H2's photodissociation was measured in the 106-136.5 nm region. The products of the radiative lifetime quenching rate constant increase with excitation wavelengths. The data obtained on lifetimes, quenchings, and fluorescence spectra point to an upper state of the C2H-asterisk fluorescence that is well bound, while the lower state is a repulsive or weak-bound state.
77 citations
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TL;DR: In this paper, a Gaussian plus biexponential decay of the solvent response function is characterized by a Gaussian plus biclastic decomposition, indicating the importance of symmetry of both the ground and excited states in determining the resulting solvent response.
Abstract: Quantum nonadiabatic molecular dynamics simulations are used to explore the molecular details surrounding photoexcitation of solvated electrons in deuterated water. The results are compared to previous studies in normal water [B. J. Schwartz and P. J. Rossky, J. Chem. Phys. 101, 6902, 6917 (1994)] to elucidate the nature of the isotope effect on both the solvation and nonadiabatic relaxation dynamics. The solvent spectral density couples differently to the individual energy levels than to the quantum energy gap, indicating the importance of the symmetry of both the ground and excited states in determining the resulting solvent response. The solvation dynamics are characterized by a Gaussian plus biexponential decay. Deuteration has little effect on the Gaussian component or long time exponential decay of the solvent response function, but a ∼20% isotope effect is observed on the faster exponential decay. The solvent response following nonadiabatic relaxation is found to be much more rapid than that follow...
76 citations