Alphazurine G and Some N,N'-Substituted Benzidines as Redox Indicators

Adams, Ralph N.; Hammaker, E. M.

doi:10.1021/ac60053a018

Cited by 9 publications

(5 citation statements)

References 15 publications

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“…However, recent laboratory measurements of the dissociative electron recombination of N 2 H + reveal that the dominant channel results in cleavage of the N-N bond (Geppert et al 2004), in contrast to previous measurements that indicated that this channel was unimportant (e.g. Adams et al 1991). This new mechanism provides a means to break apart N 2 at a faster rate than He + attack and may lead to large 15 N enhancements on the proton-transfer timescale of ∼10 5 yr.…”

Section: Introductionmentioning

confidence: 83%

Interstellar diazenylium recombination and nitrogen isotopic fractionation

Rodgers

Charnley

2004

Monthly Notices of the Royal Astronomical Society

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In an earlier paper (Charnley & Rodgers), we demonstrated that gas‐phase chemistry in selectively depleted interstellar cores and/or protostellar discs can lead to significant 15N enhancements. Recent laboratory measurements of the electron dissociative recombination of N2H+ show that this reaction is able to break the N–N bond and so will release nitrogen atoms and NH radicals into the gas at a much faster rate than previous models have assumed. We have assessed the importance of this new result for the 15N chemistry and find that the reaction acts to reduce the degree of 15N enhancement. We discuss two modifications to our original model that each allow the high 15N/14N ratios to be recovered: N2 H+ recombination on polycyclic aromatic hydrocarbon (PAH) molecules and a small barrier in the N + NH reaction. We find that higher 15N/14N ratios can be produced in this revised model. Some observational consequences of these are outlined.

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Section: Introductionmentioning

confidence: 83%

Interstellar diazenylium recombination and nitrogen isotopic fractionation

Rodgers

Charnley

2004

Monthly Notices of the Royal Astronomical Society

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“…In this Letter, we are motivated to revisit our previous models as a result of several recent discoveries. First, the experimental results of Geppert et al (2004) have been challenged by Molek et al (2007), who demonstrated that recombination of N 2 H + leads predominantly to N 2 + H, as indicated in previous work (Adams et al 1991). The new results indicate that rupture of the N 2 bond occurs rarely, if at all, with an upper limit for the NH + N 0 branching ratio of 5 per cent.…”

Section: Introductionmentioning

confidence: 93%

Nitrogen superfractionation in dense cloud cores

Rodgers

Charnley

2008

Monthly Notices of the Royal Astronomical Society: Letters

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We report new calculations of interstellar 15N fractionation. Previously, we have shown that large enhancements of 15N/14N can occur in cold, dense gas where CO is frozen out, but that the existence of an NH + N channel in the dissociative recombination of N2H+ severely curtails the fractionation. In the light of recent experimental evidence that this channel is in fact negligible, we have reassessed the 15N chemistry in dense cloud cores. We consider the effects of temperatures below 10 K, and of the presence of large amounts of atomic nitrogen. We also show how the temporal evolution of gas-phase isotope ratios is preserved as spatial heterogeneity in ammonia ice mantles, as monolayers deposited at different times have different isotopic compositions. We demonstrate that the upper layers of this ice may have 15N/14N ratios an order of magnitude larger than the underlying elemental value. Converting our ratios to delta-values, we obtain delta(15N) > 3,000 per mil in the uppermost layer, with values as high as 10,000 per mil in some models. We suggest that this material is the precursor to the 15N `hotspots' recently discovered in meteorites and IDPsComment: accepted by MNRA

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“…Good is 1) has reviewed the data available up to 1975. With the inception of the SIFT technique accurate temperature dependencies have been obtained for several ternary association reactions which indicates that the variation of the ternary rate coefficients with temperature closely conforms to a simple power law behaviour (k et T -n) as predicted by statistical theory, but with n much smaller than predicted [131][132][133]. Such data is contributing to a growing understanding of the mechanistic aspects of ion-molecule association reactions 134' 1as)…”

Section: Ternary Ion-molecule Reactionsmentioning

confidence: 71%