Electronic excitation and charge transfer processes in collisions between Mg(3 1S0) atoms and Rb+(1S0) ions in the 0.07–4.00 keV energy range

Reactive processes in gas phase Na(+)-iso-C3H7Cl collisions: experimental guided-ion-beam and ab initio studies of the reactions on the ground singlet potential surface of the system up to 12.00 eV

Reactive processes, taking place when sodium ions collide with neutral iso-C(3)H(7)Cl molecules in the 0.02-12.00 eV range of energies in the center of mass frame, have been studied using an octopole radiofrequency guided-ion-beam apparatus developed in our laboratory. A dehydrohalogenation reaction channel leading to Na(C(3)H(6))(+) formation has been observed up to 1.00 eV while another process producing NaHCl(+) continues up to 4.00 eV. Furthermore, C(3)H(7)(+) formation resulting from decomposition of the reactants, ion-molecule adducts, has also been observed as well as its decomposition into C(2)H(3)(+) on increasing collision energy. Cross-section energy dependences for all these reactions have been obtained in absolute units. The ab initio electronic structure calculations have been done at the MP2 level for the colliding system ground singlet potential surface, giving information on the reactive surface main topological features. From the surface reactants side to the products' one, different potential wells and barriers have been characterized and their connectivity along the reaction evolution has been established using the intrinsic-reaction-coordinate method, thus interpreting the dynamical evolution of the reactants' collision complex to products. Experimental results demonstrate that NaHCl(+) can be produced via different channels. Reaction rate constants at 308.2 K for both dehydrohalogenation reactions have been calculated from measured excitation functions. It has been also confirmed that the reactants adduct decomposition giving C(3)H(7)(+) and NaCl takes place on the same potential surface. A qualitative interpretation of the experimental results in terms of ab initio calculations is also given.

Experimental cross-sections energy dependence and an ab initio electronic structure survey of the ground singlet potential surface for reactive Li(+) + n-C(3)H(7)Cl collisions at low energies

Reactive collisions between n-C(3)H(7)Cl molecules and lithium ions both in their ground electronic state have been studied in the 0.05-7.00 eV center of mass energy range using an octopole radio frequency guided-ion beam apparatus developed in our laboratory and recently modified. At low collision energies, dehydrohalogenation reactions leading to Li(C(3)H(6))(+) and Li(HCl)(+) are the main reaction channels, while on increasing energies C(3)H(7)(+) and C(2)H(3)(+) formation become dominant. Cross section energy dependences in arbitrary units for all these reactions have been measured. Also, ab initio electronic structure calculations at the MP2 level have been performed to obtain information about the potential energy surface on which the reactive processes take place. The reactants' entrance channel leads to the formation of a stable [Li-n-C(3)H(7)Cl](+) ion-molecule adduct that, following an intrinsic-reaction-coordinate pathway and surmounting a transition state, isomerizes to [Li-i-C(3)H(7)Cl](+). From this second minimum, dehydrohalogenation reactions for both n-C(3)H(7)Cl and i-C(3)H(7)Cl share a common reaction pathway leading to the same products. All potential barriers explored by reactions always lie below the reactants' energy. The entrance reaction channel [Li-n-C(3)H(7)Cl](+) adduct also leads adiabatically to C(3)H(7)(+) formation which, on increasing collision energy generates C(2)H(3)(+)via a unimolecular decomposition. A qualitative interpretation of the experimental results based on our ab initio calculations is also given.

An experimental guided-ion-beam and ab initio study of the ion-molecule gas-phase reactions between Li+ ions and iso-C3H7Cl in their ground electronic state

Reactive collisions between Li(+) ions and i-C(3)H(7)Cl molecules have been studied in the 0.20-12.00 eV center-of-mass energy range using an octopole radio frequency guided-ion beam apparatus recently developed in our laboratory. At low collision energies, dehydrohalogenation reactions giving rise to Li(C(3)H(6))(+) and Li(HCl)(+) are the main reaction channels, while at higher ones C(3)H(7)(+) and C(2)H(3)(+) become dominant, all their reactive cross sections having been measured as a function of the collision energy. To obtain information about the potential energy surfaces (PESs) on which the reactive processes take place, ab initio calculations at the MP2 level have been performed. For dehydrohalogenations, the reactive ground singlet PES shows ion-molecule adduct formation in both the reactant and product sides of the surface. Following the minimum energy path connecting both minima, an unstable intermediate and the corresponding barriers, both lying below the reactant's energy, have been characterized. The entrance channel ion-molecule adduct is also involved in the formation of C(3)H(7)(+), which then generates C(2)H(3)(+) via an CH(4) unimolecular elimination. A qualitative interpretation of the experimental results based on ab initio calculations is also included.

Inelastic electronic excitation and electron transfer processes in collisions between Mg(3S01) atoms and K+(S01) ions studied by crossed beams in the 0.10-3.80-keV energy range

Inelastic and charge-transfer excitation processes in collisions between ground-state neutral Mg atoms and K+ ions have been studied by means of a crossed molecular-beam technique. Decay fluorescent emissions from Mg(3 1P1),Mg(4 3S1), and Mg(3s(1)3d(1), 3(3)D3,2,1) as well as the phosphorescent emission due to Mg(3 3P1) have been observed from excited Mg atoms and the charge-transfer emission decays from K(4 2P 3/2,1/2), K(5 2P 3/2, 1/2), K(6 2S 1/2), and K(4 2D 5/2, 3/2) for excited K atoms. The corresponding absolute cross-sections values versus collision energy functions were determined in the 0.10-3.80 keV laboratory energy range. In order to interpret the experimental results, accurate ab initio full configuration-interaction calculations using pseudopotentials have been performed for the (Mg-K)+ system, giving a manifold of adiabatic singlet and triplet potential-energy curves correlating with the different collision channels, which allow a qualitative interpretation of the emission excitation functions measured for the different processes studied. A comparative study with other Mg-alkali ion systems previously studied is also included.