Flash photolysis of

Figure Bl.16.15. TREPR spectmm after laser flash photolysis of 0.005 M DMPA (5) in toluene, (a) 0.7 ps, 203 K, RE power 10 mW O, lines CH (8), spacing 22.8 G , benzoyl (6), remaining lines due to (7). (b) 2.54 ps, 298 K, RE power 2 mW to avoid nutations, lines of 7 only. Reprinted from [42].

This technique with very high frequency resolution was used to study the population of different hyperfme structure levels of the iodine atom produced by the IR-laser-flash photolysis of organic iodides tluough multiphoton excitation ... 

Electronic excitation from atom-transfer reactions appears to be relatively uncommon, with most such reactions producing chemiluminescence from vibrationaHy excited ground states (188—191). Examples include reactions of oxygen atoms with carbon disulfide (190), acetylene (191), or methylene (190), all of which produce emission from vibrationaHy excited carbon monoxide. When such reactions are carried out at very low pressure (13 mPa (lO " torr)), energy transfer is diminished, as with molecular beam experiments, so that the distribution of vibrational and rotational energies in the products can be discerned (189). Laser emission at 5 p.m has been obtained from the reaction of methylene and oxygen initiated by flash photolysis of a mixture of SO2, 2 2 6 (1 )-... 

Flash photolysis of a 4-enamino-5-one at 650 °C generated ethylnylamine, which was stable at -196 °C and its IR spectrum was examined. Warming caused tautomerization to N-phenylketenimine (Scheme 66) (80AG743). 

In addition to the stable I2O5 and moderately stable I4O9 and I2O4, several short-lived radicals have been detected and characterized during y-radiolysis and flash photolysis of iodates in aqueous alkali ... 

Tlie existence of the ylide 19, which can formally be interpreted as the deprotonation product from the corresponding salt 7a, has been claimed by trapping chlorocarbene with pyridine during the laser-flash photolysis of e do-7-chlorodibenzo[n,c]bicyclo[4.1.0]heptane (18) (96JPC18426). Bromination of l-vinyl-2-pyridone (20) yields the bicyclic pyridinium bro-... 

This was postulated to account for the results from flash photolysis of the Cu -glutamic acid and Cu -serine systems. 

Prepd by dehydrating coned nitric acid with phosphorus pentoxide (Refs 3 4). Explds if heated suddenly (Ref 4). Can also be prepd by the flash photolysis of 02-N20-He mixts (Ref 11), and by the radiolysis of N2O4—HN03 with 7 rays (Ref 1.2)... 

The flash photolysis of s-trinitrobenzene (TNB) aerated solns in alcohols generated a transient species with absorption maxima at 430 and 51 Onm (Ref 27). The yield of the transient was a function of oxygen concn, and its rate of formation was viscosity dependent. In deaerated solns, instead of the transient, a brown permanent product, identified as a charge transfer... 

The flash photolysis-of 2,4,6-trinitrotoluene solns (TNT) indicated a photochemically induced isomerization leading to the aci-quinoid isomer... 

Nanosecond flash photolysis of 1,4-dinitro-naphthalene in aerated and deaerated solvents showed a transient species with absorption maximum at 545nm. The maximum of the transient absorption was independent of solvent polarity and its lifetime seemed to be a function of the hydrogen donor efficiency of the solvent. The transient absorption was attributed to the lowest excited triplet state of 1,4-dinitronaphthalene. Based on spectroscopic and kinetic evidence, the triplet state of 1,4-dinitronaphthalene behaved as an n - Tt state in nonpolar solvents,... 

Flash photolysis of coordination compounds. Z. Stasicka and A. Marchaj, Coord. Chem. Rev., 1977,23,131-181 (271). 

Flash photolysis. Interpret the following data for the decay of the durosemiquinone radical, produced by the flash photolysis of 10 3 M duroquinone in acidic isopropyl alcohol ... 

Simultaneous with this work, Ozin and co-workers were independently investigating other bimetallic combinations. When Cr and Mo were cocondensed (133) together in Ar, using the apparatus shown in Fig. 11, a controlled pathway to CrMo was found. This molecule had previously been observed in the gas phase (30) from flash photolysis of a mixture of Cr(CO)6 and Mo(CO)g vapors. The molecule was identified (UV-visible spectroscopy) by a series of Cr/Mo/Ar concen-... 

Flash photolysis of either H2S [66] or H2S2 [67, 68] in the gas phase at low partial pressures produces, inter aha, HS2- radicals which were detected by their UV absorption spectrum in the 307-380 nm region. In addition, singlet and triplet 2 molecules as well as SH radicals are formed from H2S2, and the following reaction mechanism has been proposed (photolysis in the region 200-300 nm in the presence of excess CO2) [67] ... 

Light can effect the coupling of phenols. For example, Joschek and Miller (22) found that phenoxyphenols could be produced in the flash photolysis of phenol, but although sought, no dioxin was detected in the reaction products. 

The u.v. maximum at 330 nm obtained after flash photolysis of tetra-phenyldiphosphine has been attributed to the PhgP radical. The spectrum of the benzophosphole system (65), like that of methylphosphole, resembles the spectrum of the corresponding pyrrole analogue. The... 

In oriented, partially dehydrated multilayers, under conditions suitable for X-ray diffraction studies, the sarcoplasmic reticulum vesicles retain much of their ATP energized Ca transport activity [200-202], The Ca transport can be initiated by flash-photolysis of P -l(2-nitro)phenyl-ethyladenosine-5 -triphosphate, caged ATP [203-208], The flash-photolysis of caged ATP rapidly releases ATP and effectively synchronizes the Ca transport cycle of the ensemble of Ca -ATPase molecules [190-192,201,209],... 

A surprising observation was made in the first experiments on the flash photolysis of CdS and CdS/ZnS co-colloids Immediately after the flash from, a frequency doubled ruby laser (X = 347.2 nm photon energy, = 3.57 eV) the absorption spectrum of the hydrated electron was recorded. This species disappeared within 5 to 10 microseconds. More recent studies showed that the quantum yield increased... 

Flash photolysis of benzoyl and naphthoyl diazomethane, which should exist in the s-cis conformation, led to ketene intermediates within the duration of the pulse ( 20 ns).241... 

Chiang, Y. Kresge, A. J. Hellrung, B. Schunemann, P Wirz J. Flash photolysis of 5-methy 1-1,4-naphthoquinone in aqueous solution kinetics and mechanism of photoenoli-zation and of enol trapping. Helv. Chim. Acta 1997, 80, 1106-1121. 

FIGURE 7.15 Time-course of the increases in amplitude of the calcium current recorded from bullfrog atrial trabeculae following (A) rapid application of the p-adrenoceptor agonist isoprenaline (3 pM), and (B) rapid intracellular release of cAMP by flash-photolysis of o-nitrobenzyl cAMP. Applications/flashes were made at time zero. (From Nargeot et al., Proc. Natl. Acad. Sci. USA, 80, 2395-2399, 1983. With permission.)... 

On flash photolysis of benzophenone in benzene two transients are observed/9-11 One of these, the shorter lived, is assumed to be the excited triplet of benzophenone, and the longer lived transient would appear to be the ketyl radical by comparison of its spectrum with that of authentic ketyl radical formed in solvents that are good hydrogen donors. This, however, may be an entirely new species which fortuitously absorbs in the same region as the ketyl radical. 

Skibsted and coworkers (Mortensen and Skibsted 1996) have shown that upon the laser flash photolysis of carotenoids in chloroform bleaching of the ground state absorption is observed and there is formation of two near infrared-absorbing species ()tmax 920 and lOOOnm for 0-CAR). The species absorbing at about lOOOnm is 0-CAR + and, as with the carotenoid/CCl302 system noted earlier, the 0-CAR,+ is formed from the other species. The nature of the other species is not defined although an adduct or a neutral carotenoid radical is proposed. 

It is not our intention in this section to provide a comprehensive review of flash photolysis of organometallic species rather, we summarize some key experiments which establish the timescales of different types of reactions. Understandably, much more work has been done on the flash photolysis of metal carbonyls in solution than in the gas phase, and so we begin with solution experiments. 

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