Kinetic spectroscopy

Szundi I, Lewis J W and Kliger D S 1997 Deriving reaction mechanisms from kinetic spectroscopy. Application to late rhodopsin intermediates Blophys. J. 73 688-702... 

The availability of lasers having pulse durations in the picosecond or femtosecond range offers many possibiUties for investigation of chemical kinetics. Spectroscopy can be performed on an extremely short time scale, and transient events can be monitored. For example, the growth and decay of intermediate products in a fast chemical reaction can be followed (see Kinetic measurements). 

Nanosecond flash kinetic spectroscopy was also carried out on 2-hydroxy benzophenone and the copolymer (11). No transients could be detected in the nanosecond time scale, suggesting that the ground state enol [S (lb) in scheme 1] has a lifetime less than 1 x 10 9 sec. These results strongly imply that processes (3) and (4) are responsible for the deactivation of singlet energy in these systems. A small, non zero triplet yield is postulated in the copolymer both to account for the photodegradation data and the transient spectral data. Triplet... 

Rubinov AN, Tomin VI, Bushuk BA (1982) Kinetic spectroscopy of orientational states of solvated dye molecules in polar solutions. J Lumin 26 377-391... 

Transient absorption techniques now have a venerable history. The development of flash kinetic spectroscopy was the work of Norrish and Porter (62). This technique typically employed a flash lamp to produce... 

Already a considerable number of transient organometallic species have been characterized by IR kinetic spectroscopy (see Table I). Like most other sporting techniques for structure determination, IR kinetic spectroscopy will not always provide a complete solution to every problem. What it can do is to provide more structural information, about metal carbonyl species at least, than conventional uv-visible flash photolysis. This structural information is obtained without loss of kinetic data, which can even be more precise than data from the corresponding uv-visible... 

Metal Carbonyl Intermediates Detected by IR Kinetic Spectroscopy... 

The development of IR kinetic spectroscopy has been challenging. Organometallic chemists have had to learn about lasers and electronics, while chemical physicists have learned about organometallic chemistry. However the final apparatus has turned out to be relatively uncomplicated and not difficult to use. We therefore anticipate that such equipment will become more widely available in the near future. 

Greiner, N.R. (1967) Hydroxyl-radical kinetics by kinetic spectroscopy. II. Reactions with C2H6, C3H8, and iso-CA IK) at 300 K. J. Chem. Phys. 46, 3389-3392. 

Vary fast reactions, both in gaseous and liquid phases, can be studied by this method. In flash photolysis technique, a light flash of very high intensity and very short duration ( 10 6 sec) is produced in the neighborhood of the reaction vessel. This produces atoms, free radicals and excited species in the reaction system. These species undergo further reactions which can be followed by spectroscopic means. The method is also known as kinetic spectroscopy. The first order rate constant as large as 105 sec-1 and second order rate constants as large as 1011 mol dm sec-1 can be measured by this technique. 

Similarly, kinetic spectroscopy studies (Figure 10.10) show the growth of absorption of Ru(bpy)j at 500 nm occurs at the same rate as the decay of luminescence of Ru(bpy)j+. 

The practice of physical chemistry came to include many subfields of research thermochemistry and thermodynamics, solution theory, phase equilibria, surface and transport phenomena, colloids, statistical mechanics, kinetics, spectroscopy, crystallography, photochemistry, and radiation. Here I concentrate only on three approaches within physical chemistry that had some promise for meeting the needs of organic chemists who wanted to explain affinity and reaction dynamics. 

Direct photo-ionization or photo-induced electron transfer from marine and terrestrial DHS to a variety of polyaromatic electron acceptors have been documented by time-resolved and steady-state laser flash kinetic spectroscopy studies under conditions which facilitate extrapolation to the environment. 

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. 

The most recent metastable defocusing technique, which is referred to as mass-analyzed ion kinetic spectroscopy (MIKES) by Beynon (77, 270, 277) and as direct analysis of daughter ions (DADI) by Maurer (278) requires the interchange of the source and collector positions in a double-focusing mass spectrometer of Nier-Johnson geometry. With... 

Greiner, N. R., Hydroxyl Radical Kinetics by Kinetic Spectroscopy. VI. Reactions with Alkanes in the Range 300-500 K, . /. Chem. Phys., 53, 1070-1076 (1970). 

Fig. 2. Block diagram of apparatus for kinetic spectroscopy in the vacuum ultraviolet.

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