Electron Induced Emission of Nitrous Oxide in the UV-VIS Spectral Range

The electron impact excitation of N2O was studied using the crossed electron-molecular beams method. Optical emission spectrum initiated by 50 eV electron impact was recorded within the range 200-700 nm. Main emission bands arise from excited ion state N2O+(A2Σ) and dissociative excitation into N2+(B2Σ+u). The rotationally un-resolved excitation-emission cross sections for selected ion transitions were scaled to absolute values and their dependence on electron energy was determined. Several of them were determined for the first time

Dissociative Excitation of Acetylene Induced by Electron Impact: Excitation-emission Cross-sections

The optical emission spectrum of acetylene excited by monoenergetic electrons was studied in the range of 190 nm to 660 nm. The dissociative excitation and dissociative ionization associated with excitation of the ions initiated by electron impact were dominant processes contributing to the spectrum. The spectrum was dominated by the atomic lines H, C and molecular bands of CH, CH, CH+, and C2. Besides the discrete transitions, we have detected the continuum emission radiation of ethynyl radical C2H. For most important lines and bands of the spectrum we have measured absolute excitation-emission cross sections and determined the energy thresholds of the particular dissociative channels

Dissociative electron attachment to c-C

The electron attachment and dissociative electron attachment to gas phase octafluorocyclobutane (c-C4F8) and to its clusters have been measured. The majority of the gas phase products were already reported earlier and have been successfully confirmed in this work. In addition, two new fragments c-C4F7− and C2F5− have been detected at electron energies ∼3.6 eV and 3.1 eV respectively. The parent molecular ion c-C4F8− has been detected not only at the expected ∼0 eV energy, but also with a weak resonance at ∼0.66 eV as well. Contrary to gas phase measurements, the electron attachment to c-C4F8 molecular clusters has been measured for the first time. The dominant ionic products at electron energies ∼0 eV are the monomer, dimer and trimer of ((c-C4F8)n=0,1,2·c-C4F8)−, ((c-C4F8)n=0,1,2·c-C4F7)− and ((c-C4F8)n=0,1,2·F)−. The higher energy resonances at ∼4 eV have been associated with the metastable c-C4F8− ion as well as with possible electron scavenging processes in clusters. Finally, above 8 eV the core-excited electron attachment has been observed

Electron-induced ionization and dissociative ionization of iron pentacarbonyl molecules

Electron ionization (EI) and dissociative ionization (DI) of Iron pentacarbonyl molecule (Fe(CO)5) was studied using a crossed molecular and electron beam mass spectrometry technique. Positive ions FeO(CO)+, FeC(CO)2+ and CO+ of Fe(CO)5 were detected for the first time. We have determined the experimental appearance energies of positive ions, the thresholds for dissociative reactions, the experimental bond dissociation energies for (CO)nFe+-CO bond breaks (for n = 4,..., 0) and their average value for Fe-C bond energy 1.25 eV in Fe(CO)5+. We have performed extensive density functional theory (DFT) studies of the ground states of neutral molecule and fragments 1 A1' Fe(CO)5, 3B1 Fe(CO)4, 3A1Fe(CO)3, 3∑g Fe(CO)2, 3 ∑FeCO as well as positive ions 2A1 Fe(CO)5+, 4A1 Fe(CO)4+, 4A1 Fe(CO)3+,  4∑g Fe(CO)2+ and 4 ∑ FeCO+. The structures and energies of the states have beendetermined and the calculated bond dissociation energies (BDEs) were compared with present experiments as well as with previous works

Formations of negative ions in Sf

Formation of negative ions initiated by interaction of thermal electrons and in the corona discharge (CD) in N2 with small admixture of SF6; was studied using the ion mobility spectrometry- orthogonal acceleration time-of-flight mass spectrometry (IMS-oaTOF) at atmospheric pressure. The negative ions have been analyzed by the ion mobility spectrometry and mass spectrometry (IMS-MS) and two-dimensional spectra (2D IMS-MS) have been recorded. We discuss the mechanisms of the negative ion formation in the N2/SF6 mixtures (0.003-0.018%) as well as the transport parameters of the ions in these mixtures. The values of the reduced ion mobilities of negative ions formed in these mixtures were determined (2.43 cm2/V s for HF2– (HF)n, 2.32 cm2/V s for NO3– (HF)n, 2.08 cm2/V s for SF5–, 2.01 cm2/V s for SOF5–, 2.00 for SOF4– 1.99 cm2/V s for SF6–, 1.83 cm2/V s for SOF5–(H2O)n and 1.73 for SOF5–(H2O)n(HF)m). The assignment of the ion mobility peaks was performed on the basis of the 2D IMS-MS spectra

Elementary processes with atoms and molecules in isolated and aggregated states

This topical issue on “Elementary processes with atoms and molecules in isolated and aggregated states” was motivated by the 6th Conference on Elementary Processes in Atomic Systems – CEPAS, which was held from July 9–12, 2014 in Bratislava, Slovakia. The conference program overlaps with the topic of this issue. The scientific papers in the topical issue cover the fields of electron, positron, ion and photon interactions with atoms, molecules and surfaces

Electron interaction with copper(II) carboxylate compounds

In the present study we have performed electron collision experiments with copper carboxylate complexes: [Cu2(t-BuNH2)2(µ-O2CC2F5)4], [Cu2(s-BuNH2)2(µ-O2CC2F5)4], [Cu2(EtNH2)2(µ-O2CC2F5)4], and [Cu2(µ-O2CC2F5)4]. Mass spectrometry was used to identify the fragmentation pattern of the coordination compounds produced in crossed electron – molecular beam experiments and to measure the dependence of ion yields of positive and negative ions on the electron energy. The dissociation pattern of positive ions contains a sequential loss of both the carboxylate ligands and/or the amine ligands from the complexes. Moreover, the fragmentation of the ligands themselves is visible in the mass spectrum below m/z 140. For the studied complexes the metallated ions containing both ligands, e.g., Cu2(O2CC2F5)(RNH2)+, Cu2(O2CC2F5)3(RNH2)2+ confirm the evaporation of whole complex molecules. A significant production of Cu+ ion was observed only for [Cu2(µ-O2CC2F5)4], a weak yield was detected for [Cu2(EtNH2)2(µ-O2CC2F5)4] as well. The dissociative electron attachment processes leading to formation of negative ions are similar for all investigated molecules as the highest unoccupied molecular orbital of the studied complexes has Cu–N and Cu–O antibonding character. For all complexes, formation of the Cu2(O2CC2F5)4−• anion is observed together with mononuclear DEA fragments Cu(O2CC2F5)3−, Cu(O2CC2F5)2− and Cu(O2CC2F5)−•. All dominant DEA fragments of these complexes are formed through single particle resonant processes close to 0 eV

Electron attachment to oxygen in nitrogen buffer gas at atmospheric pressure

We have carried out experimental and theoretical studies of three body electron attachment (TBEA) to O2 in N2/O2 mixtures. We have applied three different experimental methods to determine the apparent rate constant k for TBEA to O2 for reduced electric fields E / n from 0.5 Td up to 4.5 Td and O2 concentrations from 0.02% up to 3%. From the apparent rate constant k we have evaluated three body rate constant for electron attachment to O2 in pure O2 (kO₂) and in pure N2 (kN₂). The comparison of present data with former studies shows that the former values of kN₂ overestimated the efficiency of this reaction, while in case of kO₂ we have found agreement with earlier studies. We have solved numerically the Boltzmann equation of the electrons and calculated the values of k, kN₂ and kO₂ using well established cross sections. Using the known collision cross section set for TBEA to O2, very good agreement between calculated and measured results for kO₂ was found, while in the case of k and kN₂ we had to introduce a scaling function, which describes the decrease of the efficiency of TBEA to O2 in presence of N2 and the dependence of the scaling function on E/n was determined

Suppression of low-energy dissociative electron attachment in Fe(CO)5 upon clustering

In this work, we probe anion production upon electron interaction with Fe(CO)5 clusters using two complementary cluster-beam setups. We have identified two mechanisms that lead to synthesis of complex anions with mixed Fe/CO composition. These two mechanisms are operative in distinct electron energy ranges. It is shown that the elementary decomposition mechanism that has received perhaps the most attention in recent years (i.e., dissociative electron attachment at energies close to 0 eV) becomes suppressed upon increasing aggregation of iron pentacarbonyl. We attribute this suppression to the electrostatic shielding of a long-range interaction that strongly enhances the dissociative electron attachment in isolated Fe(CO)5