X-ray transient absorption spectroscopy

Chen LX, Zhang X, Lockaid JV et al (2010) Excited-state molecular stractures captured by X-ray transient absorption spectroscopy a decade and beyond. Acta Cryst A 66 240-251... 

X-ray Transient Absorption Spectroscopy for Solar Energy Research... 

Protonated polymethylbenzenes281 and the chlorohexamethylbenzenium cation,282 intermediates in aromatic electrophilic substitutions known as Wheland intermediates, have been isolated as crystalline salts, allowing investigators to obtain their X-ray crystal structure. Nitrosoarenium a complexes of various arenes were directly observed by transient absorption spectroscopy.283 Kochi presented a method combining appropriate instrumental techniques (X-ray crystallography, NMR, time-resolved UV-vis spectroscopy) for the observation, identification, and structural characterization of reactive intermediates fa and n complexes) in electrophilic aromatic substitution.284... 

Transient intermediates are most commonly observed by their absorption (transient absorption spectroscopy see ref. 185 for a compilation of absorption spectra of transient species). Various other methods for creating detectable amounts of reactive intermediates such as stopped flow, pulse radiolysis, temperature or pressure jump have been invented and novel, more informative, techniques for the detection and identification of reactive intermediates have been added, in particular EPR, IR and Raman spectroscopy (Section 3.8), mass spectrometry, electron microscopy and X-ray diffraction. The technique used for detection need not be fast, provided that the time of signal creation can be determined accurately (see Section 3.7.3). For example, the separation of ions in a mass spectrometer (time of flight) or electrons in an electron microscope may require microseconds or longer. Nevertheless, femtosecond time resolution has been achieved,186 187 because the ions or electrons are formed by a pulse of femtosecond duration (1 fs = 10 15 s). Several reports with recommended procedures for nanosecond flash photolysis,137,188-191 ultrafast electron diffraction and microscopy,192 crystallography193 and pump probe absorption spectroscopy194,195 are available and a general treatise on ultrafast intense laser chemistry is in preparation by IUPAC. 

Schaniel and coworkers studied the properties of the photoinduced ON and r/ -NO isomers in Na2[Fe(CN)5N0]-2H20 embedded in meso-pores of sihca xerogels by X-ray diffraction, steady-state low-temperature absorption, nanosecond transient absorption spectroscopy, and IR spectroscopy (34). They determined that the electronic structures and activation energies of these / -ON and tf -NO isomers were not dependent on the particle size (statistically distributed molecules or nanoparticles) and as such the isomers were essentially quasi-free inside the pores of the gel (34). 

The photophysics of triplet excitons in conjugated donor-acceptor copolymers e.g. fluorene, carbazole and thiophene derivatives), and their quenching by molecular ojqrgen were evaluated by transient absorption spectroscopy, and correlated with X-ray diffraction measurements of relative material crystallinity. ... 

The X-ray crystal structure of [Re(CO)3(phen)(His83)] AzCu was solved at high resolution. The rate of oxidation of Cu by photoexcited Re was measured on the protein crystal by transient absorption spectroscopy. It was found to be in... 

The term 1 or h indicates low or high coverage of adsorbed ethene, as inferred from ethene exposures.h TPD, temperature-programmed desorption LITD, laser-induced thermal desorption 1 FT-MS, Fourier-transform mass spectrometry SIMS, secondary-ion mass spectrometry MS, mass spectrometry T-NEXAFS, transient near-edge X-ray absorption fine structure spectroscopy RAIRS, reflection-absorption infrared spectroscopy. d Data for perdeut-erio species.1 Estimated value. 

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