The reactions of primary species of water radiolysis viz.e
aq
−, H-atom and OH radicals and some one electron reductants with 2,6-pyridine dicarboxylic acid were studied at various pHs. The rate ...constants for these reactions were determined and the values were found to be in the range of 0.3−1 × 10
10 dm
3 mol
−1 s
−1. Spectral, kinetic, redox and acid-base properties of the transient species were also studied. The transient species formed by e
aq
− reaction have absorption maxima around 300 and 390 nm. The pk
a values of the semireduced species were determined to be 2.1 and 5.4. These species were found to be strong reductants. The species produced by H-atom reaction was also able to reduce methyl viologen but to a lesser extent indicating that only a part of the species produced by H-atom reaction are reducing in nature. OH radicals react by addition to the pyridine ring. The transient spectra have absorption maxima around 350 and 500 nm. pK
a values of the OH adducts were determined to be 2.1 and 4.5.
Reactions of e
aq
−, H-atoms, OH, (CH
3)
2COH, and CO
2
− radicals with V(III)picolinate and Cr(III)picolinate have been studied by the pulse radiolysis technique. The spectra of V(II)picolinate, ...V(IV)picolinate, Cr(II)picolinate, OH adduct of Cr(III)picolinate and Cr(IV)picolinate have been obtained and the rate constants of the reactions of various radicals with V(III) and Cr(III)picolinate have been determined. The implications of these results to the chemical decontamination of nuclear reactor systems are discussed.
The reactions of e−aq, H-atoms, OH radicals and some one electron oxidants and reductants were studied with dithio-oxamide (DTO) in aqueous solutions using pulse radiolysis technique. The transient ...species formed by the reaction of e−aq with DTO at pH 6.8 has an absorption band with λmax at 380 nm and is reducing in nature. H-atom reaction with DTO at pH 6.8 also produced the same transient species. The semi-reduced species was found to be neutral indicating that the electron adduct gets protonated quickly. However at pH 1, the species produced by H-atom reaction had a different spectrum with λmax at 360 and 520 nm. Reaction of acetone ketyl radicals and CO2− radicals with DTO at pH 6.8 gave transient spectra which were identical to that obtained by e−aq reaction. However at pH 1, the spectrum obtained by the reaction of acetone ketyl radicals with DTO was similar to that obtained by H-atom reaction at that pH. The transient species formed by OH radical reaction with DTO in the pH range 1–9.2 also has two absorption maxima at 360 and 520 nm. This spectrum was identical with the spectrum obtained by H-atom reaction at pH 1. This means that all these radicals viz. OH, H-atom and (CH3)2COH radicals react with DTO at pH 1 by H-abstraction mechanism. The transient species produced was found to be sensitive to the presence of oxygen. One-electron oxidizing radicals such as Br2−· and SO4−· radicals reacted with DTO at neutral pH to give the same species as produced by OH radical reaction having absorption maxima at 360 to 520 nm. At acidic pHs, only Br2−· and Cl2−· radicals were able to oxidize DTO to give the same species as produced by OH radical reaction. The semioxidized species is a resonance stabilized species with the electron delocalized over the-N-C-S bond. This species was found to be neutral and non-oxidizing in nature.
Rate constants for the reactions of eaq−, H and OH radicals with 2-pyridine carboxaldehyde and 2-pyridine methanol have been determined by pulse radiolysis technique. Reactions of reducing radicals ...such as acetone ketyl radicals and CO2− with these compounds were also evaluated at various pHs. The species produced by the reaction of reducing radicals with these solutes was a strong reductant itself. While pyridinyl were produced in the case of 2-pyridine methanol, one-electron reduction of 2-pyridine carboxaldehyde led to the formation of PyCHOH radical. The one-electron reduction potential of PyCHOH radicals was estimated by establishing an equilibrium with MV+ radical cations to be −0.6V vs NHE. OH radical reaction with 2-pyridine carboxaldehyde gave an OH adduct, while in the case of 2-pyridine methanol, OH radicals reacted partly by H-abstraction from the −CH2OH group. SO4− radical reaction with 2-pyridine carboxaldehyde produced a species which was reducing in nature. The rate constants for the reaction of eaq− and OH radicals are compared with similar values obtained in the case of other 2-pyridine derivatives to see if there is any electron-inductive effect.
Thioacetamide (TA) is an organic compound having thioamide group similar to that in thiourea derivatives. Its reactions with eaq−, H-atom and OH radicals were studied using the pulse radiolysis ...technique at various pHs and the kinetic and spectral characteristics of the transient species were determined. The initial adduct formed by the reaction of TA with OH radicals at pH 7 does not absorb light in the 300–600 nm region but reacts with the parent compound to give a transient species with an absorption maximum around 400 nm. At pH 0, the reaction of OH radicals with TA directly gives a similar transient species with absorption maximum at 400 nm. Transient species formed by H-atom reaction with TA and pH 0 has no absorption in the 300–600 nm region but at higher acidity a new transient species is formed which has absorption maximum at 400 nm. This transient absorption observed in the case of both OH and H atom reaction with TA is ascribed to the formation of a resonance stabilized radical similar to that obtained in the case of thiourea derivatives. The species produced by electron reaction viz. electron adduct was found to be a strong reductant and could reduce MV2+ with a high rate constant. H2S was produced as a stable product in the reaction of eaq− and its G-value was determined to be about 0.8.
Reactions of e
aq
−, H-atoms and
OH radicals have been studied with 5-amino tetrazole (ATZ) in aqueous solution. e
aq
− reaction in the pH range 4.5–9 did not give any light absorbing transient ...species but NH
3 was obtained as a product indicating that the site for e
aq
− reaction is the −NH
2 group. In the case of
OH radical reaction, a transient spectrum with
λ
max at 340 nm was obtained at pH 7.5. An identical spectrum was produced by the reaction of SO
4
−
radicals with ATZ at neutral pH indicating that both
OH radical and SO
4
−
radical react by one electron oxidation. The rate constants for the reactions of e
aq
− and
OH with ATZ at pH 7.5 were found to be 6 × 10
7 and 5.2 × 10
9 dm
3 mol
−1 s
−1 respectively, whereas the rate constant for H-atom reaction may be < 10
7 dm
3 mol
−1 s
−1.
We investigate different physical properties of a spin imbalanced fermionic superfluid described by an attractive Hubbard model in presence of a harmonic trap. To characterize the ground state of ...such a system, we compute various correlation functions, such as pairing, density and current correlations To underscore the effect of the trap, we compute these quantities as a function of strength of the trapping potential. A distinguishing feature of a superfluid state with population imbalance, is the appearance of a phase with spatially modulating gap function, called the Fulde- Ferrell-Larkin-Ovchinnikov (FFLO) phase which is present for both with and without trap. Trapping effects induce lowering of particle density and yields an empty system in the limit of large trapping depths.
