Excimer

About: Excimer is a research topic. Over the lifetime, 3725 publications have been published within this topic receiving 75104 citations.

Effects of metal cation coordination on fluorescence properties of a diethylenetriamine bearing two end pyrene fragments.

Abstract: Fluorescence properties of a diethylenetriamine bearing two end pyrene fragments (L) have been studied in water, where effects of adding metal cations (Zn2+, Cd2+, Cu2+, Hg2+, Ag+) on the emission properties of L have been studied. Without metal cations, L shows dual-mode fluorescence consisting of monomer and excimer emissions. The monomer emission intensity (IM) is strong at acidic pH but decreases with a pH increase because of an electron transfer (ET) from the unprotonated nitrogen atoms to the excited pyrene fragment. The excimer emission is due to the static excimer formed via a direct photoexcitation of the intramolecular ground-state dimer (GSD) of the end pyrene fragments. The excimer emission intensity (IE) is weak at acidic pH but increases with a pH increase because of the GSD stability increase associated with the deprotonation of the polyamine chain. Addition of metal cations leads to IM decrease, where chelation-driven IM enhancement does not occur even with diamagnetic Zn2+ and Cd2+ at any...

Excitation mechanism for hydroxyl(A) in the argon fluoride excimer laser photolysis of nitric acid

Abstract: The involvement of an intermediate species in the excitation of OH(A) emission in the 193-nm photolysis of nitric acid is demonstrated by using two excimer lasers in a pump-probe experiment. The intermediate species is characterized both through analysis of the resulting OH(A) emission and by measurements of its collisional and lifetime properties. After careful consideration of all reasonable candidates, it is proposed that the intermediate is HONO - probably in its lowest triplet state. 37 references, 5 figures, 1 table.

Luminescence and photochemistry of 4‐thiouridine in aqueous solution

Abstract: — In bidistilled water, 4-thiouridine (4TU) exhibits a weak unusual luminescence, the quantum yield of which is 3 × 10-4 at 25°C. The excitation spectrum corresponds well to the 4TU absorption spectrum. The emission lies at longer wavelengths (Λmax 550 nm) than the 4TU phosphorescence observed at 77 K (Λmax, 470–480 nm). From the emission signal obtained after an excitation flash of 3 ns half-width, an “apparent” rate constant for the radiative deactivation process, shorter than 5 × 106 s, can be inferred. The 300 K emission is efficiently quenched by halides and by oxygen: quenching involves a long-lived intermediate (⋍ 200 ns). Clearly the emissive state X is populated through the S0-S1 electronic transition ππ* of 4TU. The nature of X cannot be unambiguously determined: it cannot be an excimer but can be either the 4TU triplet state or another chemical state distinct from the 4TU excited singlet or triplet states. An interesting finding is that the 300 K emission and the ability of 4TU to photoreact are related: they are quenched with the same efficiency by halide anions. This indicates that quenching occurs at the same long-lived intermediate species, which is either a precursor of the emitter or the emitter itself.