Effect of internal excitation on the collision-induced dissociation and reactivity of Co 2 +

Hales, David; Armentrout, P. B.

doi:10.1007/bf00703589

Cited by 117 publications

(87 citation statements)

References 44 publications

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“…The Co atoms in dimer have bonding configuration closer to 3d 8 4s 1 than that of the isolated Co atom, which is 3d 7 4s 2 and in addition to the highly delocalized 4s electrons, the more localized 3d electrons also contribute strongly to the bonding, 24 which consequently, produces a shorter bond length for the dimer. Compared to the neutral Co 2 dimer, the experimentally 23,25,26 28 We found that Co 2 dimer has a total magnetic moment of 4 µ B , which is also consistent with mass spectroscopic measurement 22 . Our estimates agree with the previous first-principles calculations.…”

Section: Resultssupporting

confidence: 81%

Structure, bonding, and magnetism of cobalt clusters from first-principles calculations

Datta¹,

Kabir²,

Ganguly³

et al. 2007

Phys. Rev. B

157

179

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The structural, electronic and magnetic properties of Con clusters (n =2−20) have been investigated using density functional theory within the pseudopotential plane wave method. An unusual hexagonal growth pattern has been observed in the intermediate size range, n =15−20. The cobalt atoms are ferromagnetically ordered and the calculated magnetic moments are found to be higher than that of corresponding hcp bulk value, which are in good agreement with the recent SternGerlach experiments. The average coordination number is found to dominate over the average bond length to determine the effective hybridization and consequently the cluster magnetic moment.

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Section: Resultssupporting

confidence: 81%

Structure, bonding, and magnetism of cobalt clusters from first-principles calculations

Datta¹,

Kabir²,

Ganguly³

et al. 2007

Phys. Rev. B

157

179

View full text Add to dashboard Cite

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“…Therefore, the use of Xe as an efficient collision gas for CID experiments can be rationalized. The relative efficiency of collisional energy transfer with Xe versus the other rare gases has been empirically demonstrated in a number of studies in our group [16,51,[62][63][64]. In some cases, we have documented that other competing reactions, e.g., charge transfer [16] or ligand exchange [65,66], can adversely affect the desired CID process, in which case, one of the lighter rare gases may prove to be a better choice as a collision gas.…”

Section: Collision Partner In Collision-induced Dissociationmentioning

confidence: 76%

Mass spectrometry—Not just a structural tool: The use of guided ion beam tandem mass spectrometry to determine thermochemistry

Armentrout

2002

J. Am. Soc. Mass Spectrom.

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172

180

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Guided ion beam tandem mass spectrometry has proved to be a robust tool for the measurement of thermodynamic information. Over the past twenty years, we have elucidated a number of factors necessary to make such thermochemistry accurate. Careful attention must be paid to the reduction of the raw data, ion intensities versus laboratory ion energies, to a more useful form, reaction cross sections versus relative kinetic energy. Analysis of the kinetic energy dependence of cross sections for endothermic reactions can then reveal thermodynamic data for both bimolecular and collision-induced dissociation (CID) processes. Such analyses need to include consideration of the explicit kinetic and internal energy distributions of the reactants, the effects of multiple collisions, the identity of the collision partner in CID processes, the kinetics of the reaction being studied, and competition between parallel reactions. This work provides examples illustrating the need to consider this multitude of effects along with details of the procedures developed in our group for handling each of them. ( W hen does a mass spectrometer become an ion beam instrument? Is this defined by the instrument, by whether the operator is an analytical or physical chemist, or by the experiments done? All mass spectrometers utilize ion beams, but the unspoken definition of an ion beam instrument is an apparatus that can be used to make quantitative physical measurements. In this regard, the capabilities of the instrumentation and the intent and training of the operator are all important factors. Whereas a mass spectrometer is often used as an identification tool through the use of mass spectral patterns, by taking advantage of the ability to easily change the kinetic energy of ions, it can also be a powerful instrument for the determination of thermodynamic data.In this article, I lay down some of the founding principles behind our use of tandem mass spectrometry, and in particular, so-called guided ion beam mass spectrometry to elucidate thermochemical information. This is achieved primarily by examining the kinetic energy dependence of endothermic ion-molecule reactions and determining their energy thresholds.Although many types of instruments have been used to perform such measurements, the link between such studies and guided ion beam techniques is a strong one. Indeed, the NIST Webbook [1] states in its section on Determinations of Reaction Endothermicity that "more commonly a so-called guided-beam apparatus is utilized for such determinations." Considering that there are only about a dozen such laboratories worldwide, this is a testament to the ability of this particular kind of apparatus to provide a plethora of high quality information. However, such information requires attention to myriad details, which are outlined in this article.Two fundamental types of reactions can be used to acquire thermodynamic information: Bimolecular exchange reactions, process 1, and collision-induced dissociation (CID), process 2.Reactions 1 can be either ex...

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“…Mass-selected (xdCyd)H + (ydCyd) protonated nucleoside base pairs are decelerated to a desired kinetic energy and focused into a rf octopole ion beam guide that radially traps ions [30][31][32] such that scattered reactant and products ions are collected efficiently as they drift toward the exit of the octopole. The octopole passes through a static gas cell where the reactant (xdCyd)H + (ydCyd) protonated nucleoside base pairs undergo collision-induced dissociation (CID) with Xe [33][34][35] under nominally single collision conditions,~0.05-0.10 mTorr. Product and unreacted (xdCyd)H + (ydCyd) ions drift to the end of the octopole, where they are focused into a quadrupole mass filter for the second stage of mass analysis.…”

Section: General Proceduresmentioning

confidence: 99%

Base-Pairing Energies of Protonated Nucleoside Base Pairs of dCyd and m⁵dCyd: Implications for the Stability of DNA i-Motif Conformations

Rodgers

2015

J. Am. Soc. Mass Spectrom.

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Hypermethylation of cytosine in expanded (CCG)n•(CGG)n trinucleotide repeats results in Fragile X syndrome, the most common cause of inherited mental retardation. The (CCG)n•(CGG)n repeats adopt i-motif conformations that are preferentially stabilized by base-pairing interactions of protonated base pairs of cytosine. Here we investigate the effects of 5-methylation and the sugar moiety on the base-pairing energies (BPEs) of protonated cytosine base pairs by examining protonated nucleoside base pairs of 2'-deoxycytidine (dCyd) and 5-methyl-2'-deoxycytidine (m(5)dCyd) using threshold collision-induced dissociation techniques. 5-Methylation of a single or both cytosine residues leads to very small change in the BPE. However, the accumulated effect may be dramatic in diseased state trinucleotide repeats where many methylated base pairs may be present. The BPEs of the protonated nucleoside base pairs examined here significantly exceed those of Watson-Crick dGuo•dCyd and neutral dCyd•dCyd base pairs, such that these base-pairing interactions provide the major forces responsible for stabilization of DNA i-motif conformations. Compared with isolated protonated nucleobase pairs of cytosine and 1-methylcytosine, the 2'-deoxyribose sugar produces an effect similar to the 1-methyl substituent, and leads to a slight decrease in the BPE. These results suggest that the base-pairing interactions may be slightly weaker in nucleic acids, but that the extended backbone is likely to exert a relatively small effect on the total BPE. The proton affinity (PA) of m(5)dCyd is also determined by competitive analysis of the primary dissociation pathways that occur in parallel for the protonated (m(5)dCyd)H(+)(dCyd) nucleoside base pair and the absolute PA of dCyd previously reported.

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Effect of internal excitation on the collision-induced dissociation and reactivity of Co 2 +

Cited by 117 publications

References 44 publications

Structure, bonding, and magnetism of cobalt clusters from first-principles calculations

Structure, bonding, and magnetism of cobalt clusters from first-principles calculations

Mass spectrometry—Not just a structural tool: The use of guided ion beam tandem mass spectrometry to determine thermochemistry

Base-Pairing Energies of Protonated Nucleoside Base Pairs of dCyd and m⁵dCyd: Implications for the Stability of DNA i-Motif Conformations

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Effect of internal excitation on the collision-induced dissociation and reactivity of Co 2 +

Cited by 117 publications

References 44 publications

Structure, bonding, and magnetism of cobalt clusters from first-principles calculations

Structure, bonding, and magnetism of cobalt clusters from first-principles calculations

Mass spectrometry—Not just a structural tool: The use of guided ion beam tandem mass spectrometry to determine thermochemistry

Base-Pairing Energies of Protonated Nucleoside Base Pairs of dCyd and m5dCyd: Implications for the Stability of DNA i-Motif Conformations

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Base-Pairing Energies of Protonated Nucleoside Base Pairs of dCyd and m⁵dCyd: Implications for the Stability of DNA i-Motif Conformations