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, the transient Raman spectra of all-trans-β-carotene in both the S 1 and T 1 states produced by direct photoexcitation were recorded by means of a recently developed, transient Ramaman technique using 355 nm pump and 532 nm probe, mode-locked and Q -switched pulse trains.
67 citations
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TL;DR: In this paper, the rovibrational state distribution of the nascent NH2(A, 2A1) fragments generated by 193.3 nm photodissociation of a room temperature sample of NH3 is determined through an analysis of a major portion (approximately 13,000 cm−1) of the NH 2(A)→X 2B1 near infrared emission spectrum obtained by time-resolved Fourier transform infrared emission spectroscopy.
Abstract: The rovibrational state distribution of the nascent NH2(A 2A1) fragments generated by 193.3 nm photodissociation of a room temperature sample of NH3 is determined through an analysis of a major portion (6000–13 000 cm−1) of the NH2(A 2A1→X 2B1) near infrared emission spectrum obtained by time‐resolved Fourier transform infrared emission spectroscopy. The NH2(A) fragments are observed to be formed predominantly in their zero‐point vibrational level, with substantial rotational excitation about their a‐inertial axis up to the limit of the available energy, ∼3150 cm−1, but with little excitation about the other axes. The pattern of this energy disposal is discussed within the framework of existing knowledge regarding the form of the NH3 A state potential energy surface on which the dissociation occurs. The essential features are entirely consistent with a direct carry over, into the fragment, of the out‐of‐plane bending vibrational motion introduced in the parent molecule by the photoexcitation process.
67 citations
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TL;DR: In this paper, the time scale of covalent state relaxation and singlet fission into triplet pairs was determined in a solution of isolated polydiacetylene chains showing a remarkably sharp excitonic transition by applying the transient transmission difference spectroscopy technique with sub-10 fs optical pulses.
Abstract: The time scale of covalent state relaxation and singlet fission into triplet pairs is determined in a solution of isolated polydiacetylene chains showing a remarkably sharp excitonic transition by applying the transient transmission difference spectroscopy technique with sub-10 fs optical pulses. Photoexcitation into the band of ionic states is followed by a branching within the first 100 fs which populates the band of covalent states. The latter start to dissociate into triplet excitations, completing the process in about 300 fs.
67 citations
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TL;DR: In this paper, high resolution photon scattering experiments on 160,162,164 Dy have revealed considerable fragmentation of dipole strength into two groups around 2.5 MeV and around 3 MeV.
67 citations
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TL;DR: In this paper, the authors used pulsed-laser-excitation/resonance fluorescence technique to assess the efficiency of OH formation following photoexcitation of NO2 at discrete wavelengths beyond the photodissociation threshold in the presence of water vapor.
Abstract: The pulsed-laser-excitation/resonance fluorescence technique was used to assess the efficiency of OH formation following photoexcitation of NO2 at discrete wavelengths beyond the photodissociation threshold in the presence of water vapor: NO2* + H2O → HONO + OH. Excitation at wavelengths between 432 and 449 nm was found to lead to OH production via a facile sequential two-photon absorption by NO2, leading to O(1D) and thus to OH in the presence of H2O, i.e., NO2 + hν → NO2*, NO2* + hν → NO2**, NO2** → NO + O(1D), O(1D) + H2O → 2OH. The cross section for the transition NO2** ← NO2* was found to be similar to that for the NO2* ← NO2 transition at 435 nm. At 532 nm, the two-photon process is not sufficiently energetic to form O(1D), and OH is not observed. An upper limit of approximately 7 × 10-5 is found for the reactive quenching of NO2* by water vapor relative to collisional quenching. The atmospheric relevance of OH formation via NO2 excitation is discussed.
67 citations