First use of the UV Super-ACO free-electron laser: Fluorescence decays and rotational dynamics of the NADH coenzyme

作者：Marie-Emmanuelle Couprie, Fabienne Mérola, Patrick Tauc, D. Garzella, A. Delboulbé, Toru Hara, Michel Billardon · 发表于：Review of Scientific Instruments · 年份：1994 · DOI：10.1063/1.1144880 · 被引用次数：81 · 研究领域：Diamond and Carbon-based Materials Research、Atomic and Molecular Physics、Advanced Electron Microscopy Techniques and Applications

Significant improvements in the performances of the Super-ACO storage ring free-electron laser (FEL) at 800 MeV have been obtained recently: enhancement of the output power in the ultraviolet, laser duration of 10 h for the same injection of positrons, long-term stability with a micropulse of 60 ps FWHM. A first series of experiments using this FEL has then been successfully performed. Taking advantage of the time structure, the polarization and the high power of the source at 350 nm, the polarized fluorescence decays of the reduced nicotinamide adenine dinucleotide coenzyme (NADH) were studied in aqueous solution, using the single-photon counting (SPC) technique. The experimental setup is described, including the Super-ACO FEL characteristics and diagnostics. The FEL working point has been first optimized by monitoring the SPC apparatus function. A complete fluorescence experiment required about 30 min of data acquisition, during which the best integrated instrumental response had a FWHM of 110 ps. Measurements performed in such a way lead to the unambiguous separation of two close lifetime components of 0.28 and 0.62 ns in the fluorescence decays of NADH at 20 °C, in good agreement with previous works. The thermodynamic parameters obtained from temperature studies show that the NADH fluorescence heterogeneity is consistent with the ground-state folding equilibrium of the coenzyme, as characterized by many other spectroscopic techniques. From the fluorescence anisotropy deca...