139 research outputs found
Proton affinity determinations and proton-bound dimer structure indications in C2 to C15, (alpha),(omega)-alkyldiamines
The 'kinetic method' was used to determine the proton affinity (PA) of a,coalkyldiamines from collision induced dissociation (CID) studies of protonated heterodimers. These PA values were consistently lower than those reported in the proton affinity scale. The apparent discrepancy was rationalized in terms of differences in the conformation of the protonated diamine monomers. The minimum energy species, formed by equilibrium proton transfer processes, have a cyclic conformation and the ion charge is shared by both amino-groups which are bridged by the proton. On the other hand, the species formed through dissociation of protonated dimers have a linear structure and the charge is localized on one of the amino-groups. Thus, the difference in the PA values obtained by both methods is a measure of the additional stability acquired by the protonated diamines through cyclization and charge delocalization. The major collision dissociation pathway of the protonated diamine monomers involved elimination of an ammonia moiety. Other reactions observed included loss of the second amino-group and several other bond cleavages. CID of the protonated dimers involved primarily formation of a protonated monomer through cleavage of the weaker hydrogen bond and subsequently loss of ammonia at higher collision energies. As observed from the CID studies, doubly charged ions were also formed from the diamines under conditions of the electrospray ionization
Atmospheric pressure chemical ionization studies of non-polar isomeric hydrocarbons using ion mobility spectrometry and mass spectrometry with different ionization techniques
The influence of ultra-high-energy cosmic rays on star formation in the early universe
The presence of ultra-high-energy cosmic rays (UHECR) results in an increase
in the degree of ionization in the post-recombination Universe, which
stimulates the efficiency of the production of H molecules and the
formation of the first stellar objects. As a result, the onset of the formation
of the first stars is shifted to higher redshifts, and the masses of the first
stellar systems decrease. As a consequence, a sufficient increase in the
ionizing radiation providing the reionization of the Universe can take place.
We discuss possible observational manifestations of these effects and their
dependence on the parameters of UHECR.Comment: 10 pages, 5 figure
Reactions of CH3OCH2+ with hydrocarbons and O, N, and S compounds: Applications for chemical ionization in selected ion flow tube studies
Insights into amine-based CO2 capture: an ab initio self-consistent reaction field investigation
Mobility resolution and mass analysis of ions from ammonia and hydrazine complexes with ketones formed in air at ambient pressure
The use of shift reagents in ion mobility-mass spectrometry: Studies on the complexation of an active pharmaceutical ingredient with polyethylene glycol excipients
Separation of different ion structures in atmospheric pressure photoionization-ion mobility spectrometry-mass spectrometry (APPI-IMS-MS)
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