Unimolecular reaction dynamics from kinetic energy release distributions.IV. Dissociation of the Pyridine ion.

in International Journal of Mass Spectrometry and Ion Processes (1999), 185-187

The kinetic energy release distribution (KERD) for the dissociation of the Pyridine ion into C4H4++HCN in the microsecond time window has been experimentally determined and theoretically analyzed by the ... [more ▼]

The kinetic energy release distribution (KERD) for the dissociation of the Pyridine ion into C4H4++HCN in the microsecond time window has been experimentally determined and theoretically analyzed by the maximum entropy method. Less energy is channeled into the reaction coordinate than the statistical estimate because of the action of the "moentum gap law". The larger the value of the relative translational momentum of the fragments, the less efficient the exploration of phase space. the fraction of phase space efficiently sampled is estimated to be of the order of 75%. [less ▲]

The Dissociative Electroionization of Carbon Dioxide by low-energy Electron Impact. The C+, O+ and CO+ Dissociation channels.

in International Journal of Mass Spectrometry and Ion Processes (1995), 144

This work reports the dissociative ionization of CO2 between 19-40 eV. The three dissociation channels producing C+, O+ and CO+ are examined in detail. Translational energy distributions as a function of ... [more ▼]

This work reports the dissociative ionization of CO2 between 19-40 eV. The three dissociation channels producing C+, O+ and CO+ are examined in detail. Translational energy distributions as a function of the impinging electron energy and the ionization efficiency for fixed kinetic energy carried away by the fragments are measured. The kinetic energy versus appearance energy diagram is obtained for the three fragment ions. When available, the present results are compared with previous measurements. The lowest appearance energy of O+ and CO+ corresponds to the predissociation of the CO2+ (C2Sigma +/g) state. At higher energies all the fragment ions are exclusively produced by the dissociative ionization of CO2 in the multiple electron transition (MET) states. Predissociation is most probably the dominant mechanism. Each MET state branches off to produce not only the three fragments but also the same fragment in two different states. This is observed for each dissociation channel, i.e. O+, CO+ and/or C+. In the latter channel no evidence is found for the dissociative ionization reaction CO2+->C++2O. [less ▲]

AN ABINITIO STUDY OF THE ISOMERIZATION AND FRAGMENTATION OF CHO2+ IONS - AN EXAMPLE OF SPIN-CONTROLLED REACTIONS

in International Journal of Mass Spectrometry and Ion Processes (1987), 77(2-3), 187-201

[CHO2+] ions exist in two isomeric forms, a quasi-linear carboxylic structure, OCOH+ (I), and a formate structure, O(CH)O+ (II). The latter is known to isomerise into the former with a low rate constant ... [more ▼]

[CHO2+] ions exist in two isomeric forms, a quasi-linear carboxylic structure, OCOH+ (I), and a formate structure, O(CH)O+ (II). The latter is known to isomerise into the former with a low rate constant (about 105 s−1). Configuration interaction ab initio calculations reveal that the ion can exist in three low-lying electronic states of different multiplicity and symmetry species, a singlet (Image 1A′) and two triplets (ã3A′ and Image 3A′'). The potential energy surfaces cross so that the nature of the lowest state varies as a function of the nuclear geometry. The singlet surface (Image 1A′) has its deepest minimum for structure I and a subsidiary minimum for structure II. The situation is reversed for the ã3A′ state which has its deepest minimum for structure II and which exhibits a shallow minimum for structure I. Thus, at low energies, the carboxylic and formate ions are respectively in a singlet and in a triplet state. These ions lose an oxygen atom on a microsecond time scale by a composite mechanism which is subject to a large isotope effect. One of the components of the metastable peak corresponds to reaction OCOH+(1A') -> O(CH)O+ (3A') -> HCO+ + O giving rise to a small kinetic energy release. The second component is due to a spin-orbit controlled direct predissociation process, viz. OCOH+ (1A') -> OCOH+ (3A') -> HOC+ + O. The probability of surface hopping varies as a function of the internal energy between 0 and a maximum value of ca. 0.008. The corresponding kinetic energy release is expected to be larger for the deuterated than for the hydrogenated compound. Thus, the two components are resolved in the deuterated compound, but hardly distinguishable in the hydrogenated species. [less ▲]

A versatile low-cost Automation System for an Electroionization Experiment.

in International Journal of Mass Spectrometry and Ion Processes (1986), 74

A cheap complete automation system designed for an electoionization experiment is described. This system is based on a Sinclair ZX Spectrum computer and a modular architecture. The control program and ... [more ▼]

A cheap complete automation system designed for an electoionization experiment is described. This system is based on a Sinclair ZX Spectrum computer and a modular architecture. The control program and general building blocks diagrams are discussed and give a general idea of how to build modules or procedures adapted to different applications. [less ▲]