Photoexcitation

About: Photoexcitation is a research topic. Over the lifetime, 5874 publications have been published within this topic receiving 134733 citations.

A Rigid Chlorin-Naphthalene Diimide Conjugate. A Possible New Noncovalent Electron Transfer Model System.

Abstract: Described in this paper is the synthesis and study of a rigid “coplanar” noncovalent electron-transfer model system. This putative noncovalent complex juxtaposes a novel donor (chlorin) and acceptor (naphthalene diimide) via a three-point hydrogen bonding interaction (CDCl3, Ka = 364 ± 47 M-1). It was studied by steady state fluorescence, time-resolved luminescence, and transient absorption methods. The results of the studies are consistent with (1) forward intraensemble electron transfer (ET) taking place rapidly following photoexcitation of the chlorin donor at 575 nm (kET = 7.6 × 108 s-1; ΔGcs ∼ −457 mV; Φ = 0.91) and (2) back electron transfer occurring even more rapidly.

Direct observation of the coherent nuclear response after the absorption of a photon.

Abstract: How molecules convert light energy to perform a specific transformation is a fundamental question in photophysics. Ultrafast spectroscopy reveals the kinetics associated with electronic energy flow, but little is known about how absorbed photon energy drives nuclear motion. Here we used ultrabroadband transient absorption spectroscopy to monitor coherent vibrational energy flow after photoexcitation of the retinal chromophore. In the proton pump bacteriorhodopsin, we observed coherent activation of hydrogen-out-of-plane wagging and backbone torsional modes that were replaced by unreactive coordinates in the solution environment, concomitant with a deactivation of the reactive relaxation pathway.

Femtosecond laser structuring and optical properties of a silver and zinc phosphate glass

Abstract: We report on the micro- and nano-structuring of a silver-containing zinc phosphate glass under high repetition rate femtosecond near-infrared laser exposure. Luminescent silver clusters are locally formed thanks to multi-photon absorption. The excitation mechanisms in the glass are investigated with a transient absorption pump-probe experiment. The free electron density of the femtosecond-laser-induced ionized material for irradiation conditions leading to structural modifications is measured. We show that the involved photo-excitation process in the laser–glass interaction is a four-photon absorption and the measured free electron density is on the order of 1017 cm− 3, four orders of magnitude below the critical electron density. The luminescence properties of these resulting structures have been investigated. Emission spectra are compared with those collected after different irradiations (γ and electron beams). The migration of silver species has been assigned to be responsible for local modifications and selective acid etching behavior of the structure.

Element-specific and site-specific ion desorption from adsorbed molecules by deep core-level photoexcitation at the K-edges

Abstract: This article reviews our recent work on the ion desorption from adsorbed and condensed molecules at low temperature following the core-level photoexcitations using synchrotron soft x-rays. The systems investigated here are adsorbed molecules with relatively heavy molecular weight, containing third-row elements such as Si, P, S, and Cl. Compared with molecules composed of second-row elements, the highly element-specific and site-specific fragment-ion desorptions are observed when we tune the photon energy at the dipole-allowed 1s→σ*(3p*) resonance. On the basis of the resonance Auger decay spectra around the 1s ionization thresholds, the observed highly specific ion desorption is interpreted in terms of the localization of the excited electrons (here called “spectator electrons”) in the antibonding σ* orbital. In order to separate the direct photo-induced process from the indirect processes triggered by the secondary electrons, the photon-stimulated ion desorption was also investigated in well-controlled m...