The first-ever femtosecond pump-probe study is reported on solvated electrons that were generated by multiphoton ionization of neat fluid ammonia. The initial ultrafast ionization was carried out with 266 nm laser pulses and was found to require two photons. The solvated electron was detected with a femtosecond probe pulse that was resonant with its characteristic near-infrared absorption band around 1.7 μm. Furthermore, the geminate recombination dynamics of the solvated electron were studied over wide ranges of temperature (227 K ≤ T ≤ 489 K) and density (0.17 g cm(-3) ≤ ρ ≤ 0.71 g cm(-3)), thereby covering the liquid and the supercritical phase of the solvent. The electron recombines in a first step with ammonium cations originating from the initial two-photon ionization thereby forming transient ion-pairs (e(am)(-)·NH(4)(+)), which subsequently react in a second step with amidogen radicals to reform neutral ammonia. The escape probability, i.e., the fraction of solvated electrons that can avoid the geminate annihilation, was found to be in quantitative agreement with the classical Onsager theory for the initial recombination of ions. When taking the sequential nature of the ion-pair-mediated recombination mechanism explicitly into account, the Onsager model provides a mean thermalization distance of 6.6 nm for the solvated electron, which strongly suggests that the ionization mechanism involves the conduction band of the fluid.
Abstract. Liquid and supercritical ammonia (NH 3 ) is photo-ionized at an energy of 9.3 eV with 100-fs duration pulses at a wavelength of 266 nm. The ionization involves two photons and generates fully solvated electrons via the conduction band of the solvent within the time resolution of the experiment. The dynamics of their ensuing geminate recombination is followed in real time with femtosecond near-infrared (IR) probe pulses. The recombination mechanism can be understood as an ion-pair mediated reaction. The electron survival probability is found to be in quantitative agreement with the classical Onsager theory for the initial recombination of ions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.