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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TL;DR: In this article, it was shown that modulated near-infrared radiation can generate terahertz plasma oscillations in the channel of a high-electron mobility transistor.
Abstract: We show that modulated near-infrared radiation can generate terahertz plasma oscillations in the channel of a high-electron mobility transistor. This effect is associated with a temporarily periodic injection of the electrons photoexcited by modulated near-infrared radiation into the transistor channel. The excitation of the plasma oscillations has the resonant character. It results in the pertinent excitation of the electric current in the external circuit that can be used for generation of terahertz electromagnetic radiation.
64 citations
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64 citations
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TL;DR: In this article, a femtosecond time-resolved multiphoton ionization technique, coupled with a reflectron time-of-flight mass spectrometer, was used to measure the lifetime of d6-acetone.
Abstract: Because of the dispute in the literature over the dissociation rate and energy partitioning of the acetone molecule upon photoexcitation to the S1 state (π*←n) and 3s Rydberg state (3s←n), we have remeasured the lifetime of acetone (also d6-acetone) on the S1 and 3s surfaces by a femtosecond time-resolved multiphoton ionization technique, coupled with a reflectron time-of-flight mass spectrometer. The measured dissociation rate of acetone on the S1 surface is prompt, and the acetyl radical is long lived. The lifetime of acetone on the 3s surface is measured to be 3.2±0.4 ps (6.0±0.5 ps for d6-acetone). The dissociation rate of acetyl is approximately 1.7 ps (2.5 ps for d3-acetyl) from the curve fitting. This agrees well with the Rice–Ramsperger–Kassel–Marcus theory predicted lifetime of 1.0 ps (1.9 ps for d3-acetyl) when the internal excitation energy of the acetyl radical is treated by a statistical-adiabatic-impulsive model.
64 citations
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TL;DR: In this paper, a theory to describe nonequilibrium electronic surface crossing during vibrational relaxation induced by ultrafast photoexcitation is developed and applied to the primary electron transfer (ET) in bacterial photosynthetic reaction centers.
Abstract: A theory to describe nonequilibrium electronic surface crossing during vibrational relaxation induced by ultrafast photoexcitation is developed and applied to the primary electron transfer (ET) in bacterial photosynthetic reaction centers. As a key concept, we define on a microscopic basis the angle between two reaction coordinates each representing the environmental nuclear displacements coupled to the initial photoexcitation (to the P* state) and to the subsequent ET processes, respectively. The “cross-spectral” density function, whose integral intensity gives the cosine of this angle, is also defined to give a consistent (nonphenomenological) description of the vibrational coherence and its dephasing. In the application to the primary ET in bacterial photosynthesis, we find (1) the time-dependent ET rate exhibits marked oscillation at low temperatures due to the nonequilibrium vibrational coherence in the P* state. However, it does not contribute very much to accelerate the primary ET rate with respect...
64 citations
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TL;DR: This work combines tunable midinfrared pump pulses with time- and angle-resolved two-photon photoemission to study ultrafast photoexcitation of the topological surface state (TSS) of Sb_{2}Te_{3}.
Abstract: We combine tunable midinfrared (mid-IR) pump pulses with time- and angle-resolved two-photon photoemission to study ultrafast photoexcitation of the topological surface state (TSS) of Sb_{2}Te_{3}. It is revealed that mid-IR pulses permit a direct excitation from the occupied to the unoccupied part of the TSS across the Dirac point. The novel optical coupling induces asymmetric transient populations of the TSS at ±k_{∥}, which reflects a macroscopic photoexcited electric surface current. By observing the decay of the asymmetric population, we directly investigate the dynamics of the long-lived photocurrent in the time domain. Our discovery promises important advantages of photoexcitation by mid-IR pulses for spintronic applications.
64 citations