Resonant Charge Transfer Reactions Research Articles

High Kinetic Energy Ion Mobility Spectrometry – Mass Spectrometry investigations of four inhalation anaesthetics: isoflurane, enflurane, sevoflurane and desflurane

Here we report the first High Kinetic Energy-Ion Mobility Spectrometry-Mass Spectrometric (HiKE-IMS-MS) investigations involving four fluranes; isoflurane, enflurane, sevoflurane and desflurane. Unlike standard (atmospheric pressure) IMS, HiKE-IMS can detect these compounds in positive ion mode. This is because its low-pressure environment (∼ 14 mbar) and the associated short ion drift times in the HiKE-IMS ensure the reagent ions O2+• and H3O+ are present in the reaction region, and these can react with the fluranes by dissociative charge and proton transfer, respectively. However, their ion intensities are very dependent on the value of the reduced electric field (E/N) applied and the humidity of the air in the reaction region of the HiKE-IMS. In this paper we explore the potential use of HiKE-IMS for air quality control and breath analysis of fluranes. To help in the interpretation of the ion mobility spectra, and hence the ion-flurane chemistry occurring in reaction region, a HiKE-IMS was coupled to a Time-of-Flight Mass Spectrometer so that the m/z values of both the reagent and product ions that are contained within the various ion mobility peaks observed could be identified with a high level of confidence. The dependencies of the intensities of these ions as functions of E/N (30–115 Td) and humidity in the reaction region are reported. A number of product ions have been observed only under low humidity conditions (H2O volume-mixing ratio ∼ 100 ppmv), including CHF2+ and CHFCl + for isoflurane and enflurane, CHF2+, CF3+ and C3H2F5O+ for desflurane, and CH3O+, CHF2+, C3H3F4O+, C4H3F6O+ and C4H3F6O+(H2O) for sevoflurane. It is interesting to note that CH3O+, CHF2+, CHFCl+ and CF3+ have shorter drift times than that measured for O2+•. This is explained by resonant charge transfer reaction processes occurring in the drift region: O2+• + O2 ⇌ O2+•.O2 ⇌ O2 + O2+•.

Formation of cations and anions upon electron interaction with (doped) helium droplets

Superfluid helium droplets have provided a new perspective for studying electron induced chemistry at extremely low temperatures. Helium droplets represent an ideal environment for the formation of novel and exotic agglomerates of atoms and molecules. Mass spectrometry can be used to detect the resulting ions formed upon electron ionization and electron attachment to doped droplets. In the case of electron ionization a helium atom of the droplet is ionized initially and after few resonant charge transfer reactions between helium atoms the charge finally localises on the dopant. An alternative process is Penning ionization of the dopant, where the scattered electron first electronically excites a helium atom on the surface of the droplet. The attachment of a low energy electron leads to formation of an electron bubble inside the droplet which decays by autodetachment or localization on a dopant, if present in the droplet. In the present minireview a general overview about the field of electron scattering with doped helium droplets is given and a presentation of important recent results related to these electron collision studies is given as well.

On the ion and neutral atom bombardment of the growth surface in magnetron plasma sputter deposition

The energy distribution of positive argon ions bombarding the substrate during radiofrequency magnetron sputter deposition has been measured as a function of the argon pressure. The results are related to measurements of the plasma potential distribution and understood invoking the occurrence of resonant charge transfer reactions. This effectively lowers the ion bombardment energy and causes the bombardment of the growth surface with neutrals of a few eV kinetic energy in the pressure range of 0.1–1Pa.

Charge transfer reactions between D +, O +, Ar +, Kr + and Xe + with CH 4, C 2H 6 and C 3H 8 at relative energies 1–10 eV

Fifteen asymmetric resonant charge transfer reactions, involving the five title atomic ions A + and the three title molecules B have been studied in the relative (center-of-mass) energy range 1–10 eV. Two different tandem mass spectrometers were used to measure limiting cross-sections at the highest energies. Time-of-flight and retarding-potential-analysis techniques were used to characterize the contribution from non-resonant processes, occurring with momentum transfer at low impact parameters. An attempt is made to correlate the magnitudes of the cross-sections for A + + B → products with molecular parameters of the original reactants: (i) the Franck—Condon factors for B → B +, and (ii) the cross-section for A + + A → A + A +. The Franck—Condon factors for B → B + are shown not to correlate quantitatively, although a propensity rule — low factors legislate low cross-sections — does apply. The dependence of the cross-section on the nature of A correlates qualitatively with the square root of the symmetric charge transfer cross-section for A + + A → A + A +. The incorporation of all these factors, within the context of Förster theory (which treats the transfer of excitation energy A ∗ + A → A + A ∗ ), is considered for charge transfer. Qualitative but not quantitative correlations are found, and a formal justification for this is noted. The implications of these results for the mechanism of these reactions at thermal energies are briefly considered.

The spectrum of singly ionized yttrium, Y II

Hollow-cathode spectra of yttrium have been registered in the wavelength region 1000-48 800 Å. Resonant charge transfer reactions in the light source favour the excitation of Y II, where 174 new levels have been established by means of 1284 newly classified lines. Altogether we report 1521 lines between 235 levels in Y II. The ground complex (4d + 5s)2 is now completely known and a number of Rydberg series have been extended. The new levels belong to the 4dnl (nl = 7s, 8s, 9s, 6p, 7p, 4d, 5d, 6d, 7d, 8d, 4f, 5f, 6f, 7f, 5g) and 5snl (nl = 7s, 8s, 6p, 6d, 4f, 5f) configurations. Eigenvector compositions, based on parametric calculations including configuration interaction, are given for all levels. The ionization limit has been determined to 98 590 ± 5 cm−1.

Observation of fine-structure transitions in rare gas charge transfer at surprisingly low energies using a crossed-molecular beam technique

The crossed-beam method was used to investigate the charge-transfer reaction of Kr +( 2P 3 2 ) with Kr( 1S 0), using a nearly pure Kr +( 2P 3 2 ) ion beam. The resonant charge-transfer reaction is well described by a standard theoretical rectilinear-trajectory model. The endoergic fine-structure transition with Δ J = 1 was also detected. This product is scattered at a definite angle, suggesting a short-range interaction which selects a particular impact parameter. Both channels are in general accord with accepted theories for ion/atom charge exchange, but the energy range at which the endothermic channel is observed is much lower than predicted.

Crossed‐Molecular beam studies of the state‐to‐state reaction dynamics of charge transfer at low and intermediate energy

AbstractThe microscopic, state‐to‐state reaction dynamics of charge transfer reactions are reviewed for the two system N(N2, N2)N and Ar+(N2, Ar)N. The crossed molecular beam method demonstrates that the symmetric, molecular case proceeds by two mechanisms at low collision energy (< 0.7 eV). One of these involves an orbiting complex in which the total available energy is redistributed, essentially statistically. The second mechanism is a direct mechanism which involves nearly rectilinear trajectories and corresponds to exactly resonant charge transfer at low energy (0.7 eV) and charge transfer accompanied by vibrational excitation at higher energy (> 10 eV). The orbiting mechanism is dominant at low energies and disappears entirely with increasing collision energy. The unsymmetric, nearly resonant charge transfer reaction is direct at all energies. At very low collision energy (0.6 eV) and moderate collision energy (> 1.5 eV) the dominant reaction channel is the generation of N2+(X2 g, v = 1) with little rotational excitation. At 0.6 eV substantial angular scattering (including back‐scattering) is observed; above 1.5 eV the trajectories are essentially rectilinear. At intermediate energies (0.8 < E < 1.3 eV) a very different mechanism is observed. All the energetically accessible vibrational states of N are formed, each with a preferred scattering angle at a given energy. Related experiments and theoretical models which rationalize some, but not all, of these results are described. The most intriguing puzzle is the “energy window” in which quantum‐state specific, angular‐specific reactive scattering is observed.

Near resonant charge transfer in the reaction F++CO→F+CO+

Charge transfer reactions in the F++CO system were investigated using a F+ ion beam in the energy range 10–300 eVlab. The electronically excited product CO+ (A 2Πi) was observed by the emission from the A→X transitions. At low collisional energy the dominant product is in the vibrational level v′=5. The reaction cross section σ(5) is about 1 Å2 at 12 eVc.m. and decreases with increasing collision energy. The large cross section at v′=5 can be interpreted by near resonant charge transfer reactions. The rotational temperature of the product is about 300 K, which is the temperature of the reactant CO gas. For the resonant charge transfer, the translational energy is not effective, but the electronic and vibrational energy couple with each other strongly.

Resonant charge transfer reactions in neon, argon, and krypton

Resonant charge transfer reactions in neon, argon, and krypton