Search

Structural aspects as well as the stability and reactivity of the CHB(r.sup.2+) dication are studied experimentally and theoretically. Translational energy distributions of the CHB(r.sup.+) products from charge transfer between CHB(r.sup.2+) and Kr indicate that the dication exists in two isomeric forms, H-C-B(r.sup.2+) and C-Br-(H.sup.2+).

Study is carried out to investigate the interaction of C(sub 2)H(sub n)(super +) (n = 2-5) hydrocarbon ions and some of their isotopic variants with room-temperature and heated highly oriented pyrolytic graphite (HOPG) surfaces. Results of scattering experiments on collisions of C(sub 2)H((super +.) (C(sub 2)D(sub 2)(super +.)), C(sub 2)H(sub 3)(super +), C(sub 2)H(sub 4)(super +.), and C(sub 2)H(sub 5)(super +) with room-temperature and heated surfaces of highly oriented pyrolytic graphite in the collision energy range 10-45 eV are reported.

Collisions of N+ and N2+ with C3 hydrocarbons, represented by a self assembled monolayer of propanethiol on a polcrystalline gold surface, were investigated by experiments over the incident energy range between 5 eV and 100 eV. For N+, formation of HCN+ is observed at incident energies of projectile ions as low as 20 eV. In the case of N2+ projectile ions, the yield of HCN+ increased above zero only at incident energies of about 50 eV. This collision energy in the laboratory frame corresponds to an activation energy of about 3 eV to 3.5 eV. In the case of N+ projectile ions, the yield of HCN+ was large for most of the incident energy range, but decreased to zero at incident energies below 20 eV. This may indicate a very small energy threshold for the surface reaction between N+ and C3 hydrocarbons of a few tenths of an eV. Such a threshold for the formation of HCN+ may exist also for collisions of N+ with an adsorbed mixture of hydrocarbon molecules. [ABSTRACT FROM AUTHOR]

The QCISD and QCISD(T) quantum chemical methods are used to characterize the energetics of various mechanisms for the formation of HC[F.sub.2.sup.+] from the bond-forming reaction of C[F.sub.3.sup.2+] with [H.sub.2]. The experimentally determined kinetic energy releases for both the channels are in good agreement with the calculated mechanisms leading to the product asymptotes.

The potential energy surface of the CHCl(super plus2) + D2 system is investigated, to determine the reaction pathways. Energies of located stationary points on the potential energy hypersurface were refined by the G2 method. The heats of formation of the reaction dications HCCl(super 2+) and CClH(super 2+) and all the relevant product ions were calculated.

Chemical reactions and charge-transfer processes in the CHCl(super 2+) +D2 systems are investigated in crossed-beam scattering experiments. Theoretical calculations of the energetics of the species involved complements the experimental data and the calculations of stationary points on the dication potential energy surfaces support the experimental data.

Single-electron charge transfer between He2+ and NH3 and H2S was investigated at the projectile energy of 70 eV by the translational energy spectroscopy method with a resolution of 120 meV. The products were He+*(2P) and the ground state molecular ion. Populations of the vibrational states of the molecular ion were derived from the spectra. The vibrational state distributions differ only slightly from the distributions obtained by photoelectron spectroscopy and the differences can be qualitatively accounted for by distortions of the equilibrium configuration of the target molecule by the approaching ion projectile. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The dynamics of CH+4 and CH+3 ion formation in collisions of Kr+ (2P3/2’1/2) with thermal CH4 has been investigated in a crossed beam experiment at a hyperthermal collision energy of 1.18 eV. The scattering data show that the CH+4 product is formed in a near-resonant exoergic process in which the most probable energy transferred to the target is practically equal to the recombination energy of the Kr+ projectile (resonant energy transfer); in addition a wide band of internal states of CH+4 up to ±0.6 eV is populated in inelastic and superelastic collisions. In contrast, the CH+3 product is formed in dissociative charge transfer, with about one-half of the yield due to nonresonant, endoergic collisions of Kr+ (2P3/2). The other half of the CH+3 product is found to originate in near-resonant exoergic collisions of Kr+ (2P1/2). An estimate is given of the distribution of the total energy deposited in methane by the above processes. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A crossed-beam study of the reaction CH+4(CH4,CH3)CH+5 was carried out in the collision energy range 0.6–2.3 eV. Three distinct patterns were observed, which may be interpreted in terms of three competing mechanisms for CH+5 formation: proton stripping, H-atom pickup, and intermediate complex decomposition. The existence of a C2H+8 intermediate, stable towards dissociation, is suggested by the results. The relative weights of the three mechanisms were estimated as a function of collision energy. [ABSTRACT FROM AUTHOR]

Total cross sections of the title reaction studied at collision energies 0.6–3 eV by the TESICO method were found to decrease by about 1.6 times as the internal energy of the reactant ion is increased from 0.1 to 1 eV. Branching ratios of collisional mechanisms were derived from isotope labeling studies: with decreasing total initial energy (sum of collision energy and reactant ion internal energy) from 4 to 0.9 eV the fraction of the dominant proton transfer mechanism slightly decreases, the fraction of H-atom transfer is almost constant, and the fraction of intermediate complex formation increases from about 5% to 15%. Significant isotope effects were observed in the impulsive proton and H-atom transfer mechanisms depending on whether the transferred particle was H or D. The charge transfer channel represents about 10%–50% of the chemical reaction channel. [ABSTRACT FROM AUTHOR]

Energy transfer in ion-surface interactions between ethanol molecular ion and self-assembled monolayers formed by perfluoro-hydrocarbon (CF-SAM), hydrocarbon (CH-SAM), and hydrocarbon with terminal -COOH group C11 or C12 chains were investigated over the incident energy rate of 11-32 eV for several incident angles.

A study was conducted to investigate the interaction of small hydrocarbon ions, CD3(super +), CD4(super +), CD5(super +), and their isotopic variants CH(sub n)(super +) and (super 13)CH(sub n)(super +) (n = 3,4,5), with room temperature and heated carbon surfaces, over the collision energy range 16-52 eV. The result shows the ion survival probability to about 10% for CD5(super +) and about 30-60 times smaller (0.2-0.4%) for CD3(super +) and CD4(super +).

Chemical reactions and charge-transfer processes in the system CO2(super 2+) + D2 is investigated in crossed-beam scattering experiments. The chemical product CO2D(super +) is formed in a nondissociative chemical reaction leading to CO2D(super +) + D(super +) through two channels that released different amounts of translational energy through decomposition of intermediates.