Flash Photolysis Of Aqueous Solutions Research Articles

Radiation chemistry of xenon trioxide, xenate and perxenate, and photochemistry of perxenate. A pulse radiolysis and laser flash photolysis study

Unstable species containing xenon in the formal oxidation states five, XeV, and seven, XeVII, were observed by pulse radiolysis of aqueous solutions of xenon trioxide, XeO3, at pH 8–9 and of xenate, HXeO–4, at pH 11–13. XeVII and species containing xenon in the formal oxidation state nine, XeIX, were observed in pulse radiolysis and flash photolysis of aqueous solutions of perxenate, HXeO3–6, at pH 11–13. The formulae HXeO3 and H3XeO2–7 are assumed for XeV and XeIX, whereas the observations suggest that XeVII corresponds to three different species for which the formulae HXeO4, HXeO2–5 and H3XeO2–6 are assumed. HXeO3 and H3XeO2–6 are formed in reactions of the hydrated electron with XeO3 and HXeO3–6, respectively. HXeO4 and H3XeO2–7 are formed in reactions of the hydroxyl radical with XeO3 and HXeO3–6 in which the hydroxyl radical adds to a ligand oxygen atom to form peroxy compounds. HXeO2–5 is formed in a reaction with the hydroxyl radical anion in which the hydroxyl radical anion adds to the xenon atom and by photolysis of HXeO3–6: HXeO3–6 [graphic omitted] HXeO2–5+ O–. XeV, XeVII and XeIX and corresponding iodine species in the oxidation states four, six and eight have similar spectra and kinetics of disappearance. Estimated values of standard Gibbs energy of formation of the xenon species are used for selecting thermodynamically feasible mechanisms for one-electron reduction of perxenate and for the decomposition of perxenate in acid solution.

Triplet state of protoporphyrin IX

Flash photolysis of aqueous solutions of protoporphyrin IX at pH values below 2 results in strong triplet state absorptions while at any higher pH, including physiologically relevant values, no triplet state formation can be detected.

Transients in the flash photolysis of aqueous solutions of tris(2,2'bipyridine)ruthenium(II) ion

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTransients in the flash photolysis of aqueous solutions of tris(2,2'bipyridine)ruthenium(II) ionDan Meisel, Max S. Matheson, W. A. Mulac, and Joseph RabaniCite this: J. Phys. Chem. 1977, 81, 15, 1449–1455Publication Date (Print):July 1, 1977Publication History Published online1 May 2002Published inissue 1 July 1977https://doi.org/10.1021/j100530a004RIGHTS & PERMISSIONSArticle Views267Altmetric-Citations67LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

FLASH PHOTOLYSIS OF TRYPTOPHAN AND N‐ACETYL‐L‐TRYPTOPHANAMIDE; THE EFFECT OF BROMIDE ON TRANSIENT YIELDS

Abstract— The initial yields of the cation and neutral radicals and the triplet are greatly enhanced when high concentrations of Br‐ are present during the flash photolysis of aqueous solutions containing either tryptophan or N‐acetyl‐L‐trytophanamide. The present study is an attempt to elucidate the mechanism by which Br‐ induces these effects. The results obtained indicate that the initial event involves an interaction between the fluorescent state and Br‐ to promote the formation of a long‐lived radical precursor that may be the triplet. It is shown that all of the Br‐‐induced neutral and cation radical formation originate from this long‐lived state. Furthermore, it was found that the mechanism of radical production from the Br‐‐induced long‐lived precursor does not involve hydrated electron formation.

Kinetics of proton transfer reactions involving hydroxypyrene-trisulphonate in aqueous solution by nanosecond laser absorption spectroscopy

A quantitative study is presented of the proton transfer reactions ▪ which follow the dissociation of the 8-hydroxypyrene-1,3,6-trisulphonic acid ion ROH by flash photolysis in aqueous solution. The value of the rate constant k 1 = 1.9 × 10 11 M −1 s −1 is in agreement with the Debye theory for diffusion controlled reactions. The rate constant k 2 is determined for a series of neutral acids AH (maleic, acetic, phenylacetic, benzoic, formic, chloroacetic, and bromoacetic acid) added to the solution. For the weaker acids (pK > 4.25) the value of log k 2 is porportional to that of pK; for those with pK < 4.25 a limiting value k 2 = 3.6 × 10 9 M −1 s −1 is reached.

Flash photolysis of aqueous solutions of cysteine

Flash photolysis of aqueous solutions of cysteine

Flash photolysis of aqueous solutions of rhodamine 6Zh

In pape r s dealing with the genera t ion c h a r a c t e r i s t i c s of solutions of Rhodamine 6Zh [1-8], i t is shown that in ce r t a in conditions t r i p l e t t r i p l e t absorp t ion and photochemical r eac t ions can make an i m por tan t contr ibution to the induced l o s s e s . However , t h e r e a r e no l i t e r a t u r e data on the pho tochemis t ry of the dye and t he r e is ve ry l i t t le informat ion on the spec t ro scopy of the t r ip le t s ta te . The extinct ion coeff icient of T T absorp t ion has been de t e rmined by f lash photolysis [9] and by calculat ion f r o m the amp l i f icat ion s p e c t r u m [10].

ELECTRON TRANSFER FROM THE EXCITED STATE OF TYROSINE TO COMPOUNDS CONTAINING DISULFIDE LINKAGES

Abstract— The flash photolysis of aqueous solutions of tyrosine has been studied in the presence of various concentrations of the cyclic disulfide sodium lipoate (thioctic acid, Na+ salt). In addition to the formation of phenoxyl radicals and hydrated electrons (and possibly H atoms) from the photoionization of tyrosine, the characteristic spectrum of the radical anion RSSR‐ of lipoate was also observed in neutral as well as in alkaline solutions. From the dependence of these yields upon the concentration of lipoate, it was found that a long–lived triplet excited state of tyrosine, rather than the singlet excited state, is involved in these reactions. The negative radical ions RSSR‐ are formed by two distinct pathways: (a) Na+–lipoate reacts with the solvated electrons which are ejected from the tyrosine triplets 3Tyr → RO.+e‐aq+ H+ followed by e‐aq+ RSSR → RSSR‐, and (b) by direct interaction of lipoate with triplet excited tyrosine, resulting in the transfer of a negative charge from tyrosine to the disulfide linkage. At high lipoate concentrations, the singlet excited state of lipoate is quenched, k4= 1.6 × 1010M‐1 sec‐1, but this reaction does not lead to the formation of RSSR‐ radical ions.

Flash photolysis of the nitrate ion in aqueous solution: excitation at 200 nm

The flash photolysis of aqueous solutions of the nitrate ion at 200 nm has been studied. Spectroscopic observations show that no solvated electrons are produced but that three transient absorption spectra appear with maxima at <260, 300, and 450–500 nm. On the basis of kinetic measurement made at various pH Values of the initial solution coupled with product analyses, these spectra have been attributed, respectively, to undissociated peroxy-nitrous acid (tentative attribution), the peroxynitrite anion, and nitrtogen dioxide. Results obtained support the hypothesis that the following primary photolytic process occurs: NO3– [graphic omitted] (NO3–)* [graphic omitted] NO2+ OH + OH– The recombination of NO2 and OH in the solvent cage gives peroxynitrous acid; this then dissociates, to give the anion. A pK value of 6·0, has been determined for peroxynitrous acid and, assuming that the rate of disappearance of peroxynitrite is controlled by the reaction, ON·O·OH → NO3–+ H+ the rate constatn of this reaction at room temperature is 1·5 ± 0·2 s–1. The origin of molecular oxygen as a product is examined.

Transient Species Produced in the Photochemistry of 5-Bromouracil and Its N-Methyl Derivatives

The flash photolysis of aqueous solutions of 1-methyl-5-bromouracil, 3-methyl-5-bromouracil, and 1, 3-dimethyl-5-bromouracil has been studied as a function of pH, in the presence and absence of oxygen and nitrous oxide. In neutral solutions, the main primary photolytic process is the formation of Br atoms and the corresponding debrominated uracil radical. Two transient species with maxima at ∼ 320 and 420 nm are formed and are suggested to be the ketyl radicals of the corresponding barbituric acid at the C2 and C4 positions, respectively. These ketyl radicals have as precursor the debrominated uracil radical. Results obtained from pulse radiolysis are used in support of this assignment. In alkaline solutions, in addition to debromination, photoionization of the anions of 5-bromouracil and of 3-methyl-5-bromouracil at the C2 position occurs with the formation of eaq− and the C2–alkoxy radical. The anion of 1-Me-5-BU at the C4 position and 1, 3-dimethyl-5-BU do not photoionize. Transient spectra obtained in the flash photolysis of 5-bromouracil atpH 13.0 are given and discussed.

Flash photolysis of aqueous solutions of azide and nitrate ions

Flash photolysis of aqueous solutions of azide and nitrate ions

The flash photolysis of aqueous solutions of halate ions

XO2 radicals are formed in the flash photolysis of XO3– ions.

Photochemical Generation of the Hydrated Electron

A transient species with properties similar to the hydrated electron produced previously by electron irradiation has been observed by flash photolysis of aqueous solutions of inorganic salts and aromatic compounds including amino acids.