Transient absorption spectroscopy experiment

The photophysics of fluorophores undergoing photoinduced charge transfer and/or internal rotation(s) is often complex. Time-resolved fluorescence experiments, transient absorption spectroscopy measurements, quantum chemical calculations, and comparison with model molecules are helpful in understanding their complex photophysical behavior. 

In the experiment, ZnCcP is produced by laser photolysis, then transient absorption spectroscopy follows the formation (k ) and decay (/Ceb) of ZnCcP + in wild-type and mutant crystals. Kang and Crane have studied the effects of interface mutations on electron transfer rates in single crystals using complexes between a zinc-substituted cytochrome c peroxidase (ZnCcP) and site-directed mutants of yeast cytochrome c (yCc).The mutants replaced the... 

Only three experiments involving transient absorption were found, probably because the populations required for a good signal to noise ratio require more powerful and therefore more expensive lasers. One of these used transient absorption spectroscopy to study ozone formation (26), making this an... 

Photoinduced electron injection is by no means a new development. This process has already been applied in areas such as silver halide photography. In this discussion, only sensitized TiC>2 surfaces will be considered. Many experiments have shown that the charge injection into the semiconductor surface is very fast. In order to study these processes, fast spectroscopic techniques are preferred. Whether or not charge injection takes place can be studied conveniently on the nanosecond time-scale by using transient absorption spectroscopy. However, to address the injection process directly, experiments are carried out on the femtosecond time-scale, while recombination and charge separation require the nanosecond to microsecond range. 

Conclusive evidence for the cation intermediate was obtained by detection of the absorption spectra of several diarylmethyl cations following nanosecond or picosecond laser flash photolysis of their respective diazo, diphenylazi-ridinylimine, or 3H-indazole precursors in acidic media [107-112], Photochemically generated vinyl carbenes were recently shown to similarly protonate by deuterium labeling experiments to give allylic cations that were detected by transient absorption spectroscopy [113],... 

In this chapter we focus on the application of trilinear models in fluorescence spectroscopy, because that is where we have most experience. However, these trilinear models are also applicable to other kinds of excited-state spectroscopy, such as transient absorption spectroscopy. Along the way, we also discuss bilinear and other models, including global analysis. ... 

Electrochemical techniques can provide exquisite information with relatively simple experiments, even for more complex systems. A recent report by Tommos has demonstrated the applicability of such electrochemical analyses to assess the role of PCET (concerted or otherwise) in the model protein 3Y using a Pourbaix diagram (Fig. 20) [154, 155]. In this system, the tyrosine residue is positioned inside a protein matrix in a desolvated and well-structured environment Voltammetric study of its oxidation displays a reversible square-wave and differential pulse voltammogram under basic conditions. The tyrosine residue in question exhibits a potential of 0.910 and 1.070 against NHE at pH 8.5 and 5.5, respectively [156]. Based on expected rate constants for side reactions associated with square-wave voltammetry [157, 158], the authors initially suspected the radical species in question must have a lifetime of at least 30 ms in collaboration with Hammarstrom, transient absorption spectroscopy has placed the half-life somewhere between 2 and... 

Pump probe spectroscopy transient absorption spectroscopy is the most widely applied method of probing excited state dynamics. In these experiments, a laser pulse (pump, C0p ) places the nanostructure into the excited state a second... 

Pump-probe absorption experiments on the femtosecond time scale generally fall into two effective types, depending on the duration and spectral width of the pump pulse. If tlie pump spectrum is significantly narrower in width than the electronic absorption line shape, transient hole-burning spectroscopy [101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112 and 113] can be perfomied. The second type of experiment, dynamic absorption spectroscopy [57, 114. 115. 116. 117. 118. 119. 120. 121 and 122], can be perfomied if the pump and probe pulses are short compared to tlie period of the vibrational modes that are coupled to the electronic transition. 

In flash spectroscopy a second spectroscopic flash is fired a short time after the photolysis flash and the transient absorption spectrum is registered on a photographic plate (Fig. 13). Repeating the experiments with different delay times gives complete information about the wavelength and the time behavior of the intermediate absorptions. 

In kinetic spectroscopy a continuous liglit source is used. The transient signal at a fixed wavelength is detected with a photomultiplier and displayed on a storage oscilloscope. Repeating the kinetic experiments at several wavelength positions again allows us to determine transient absorption spectra. 

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