Collisions Of Slow Electrons Research Articles

Negative Ion Binding Energies in Complex Heavy Systems

We review briefly the recent progress in the determination of accurate and reliable electron affinities (EAs) of complex heavy systems with the view of assessing the reliability of the existing measured and/or calculated EAs of these systems. We demonstrate using slow electron collisions with complex heavy systems a novel and robust approach to the determination of reliable EAs from negative ion formation. From the Regge-pole calculated elastic total cross sections (TCSs), characterized by Ramsauer-Townsend (R-T) minima, shape resonances and dramatically sharp resonances manifesting anionic formation, we extract the anionic binding energies (BEs) for the ground, metastable and excited anionic states formed during the collisions. The ground state anionic BEs located at the absolute values of the R-T minima are identified with the systems’ EAs. Results for various complex heavy systems, including fullerene molecules are compared with available measurements and calculations.

Collisions of Slow Electrons with Thymine Molecules

Using a hypocycloidal electron spectrometer, the total scattering cross section of slow (0–9 eV) electrons and the dissociative electron attachment cross section for thymine molecules in the gas phase were measured. The ionization cross section for a thymine molecule was studied in the energy range of 9–32 eV. Some features were found in the scattering cross section, caused by the formation and decay of short-lived states of the molecular negative ion. Three of them (E = 0.32, 1.71, and 4.03 eV) relate to shape resonances; the others, which are observed for the first time, refer to the Feshbach resonances (or core-excited resonances). In the total dissociative attachment cross section in the energy range of E < 4 eV, a clear structure is observed due to the formation of a negative ion (T–H)–, and a less intense structure associated with the total contribution of fragment thymine ions is found above 4 eV. The correlation of the features found in the total scattering cross section and in the dissociative attachment cross section is assessed. The absolute total scattering cross section was obtained by normalizing the measured curve to the theoretical calculation. In the total ionization cross section, features are observed that are associated both with the effect of the formation of fr-agment ions and with ionization due to the ejection of electrons from the orbitals of the outer shell of the molecule.

Low-energy collisions between electrons and hydrogen fluoride cations

We have studied slow electron collisions with hydrogen fluoride cations in the framework of multi-channel quantum defect theory. Assuming energy-independent interactions, the short-range reaction matrix has been evaluated in the second order of the Born expansion of the Lippmann–Schwinger equation. The isotopic effects on the cross sections and thermal rate coefficients for dissociative recombination, vibrational excitation and de-excitation have been investigated.

Dissociative Excitation of the Odd Sextet Levels of the Cobalt Atom by Collisions of Electrons with Cobalt Dichloride Molecules

Inelastic collisions of slow electrons with cobalt dichloride molecules, leading to the formation of excited cobalt atoms in odd sextet states, are experimentally studied. At an incident electron energy of 100 eV, thirty six dissociative excitation cross sections are measured for levels belonging to the z6D°, z6F°, and z6G° terms. In the electron energy range of 0–100 eV, ten optical excitation functions are recorded. The full cross sections for the dissociative excitation of the cobalt atom levels and the contribution of cascade transitions to their population are determined. The cross sections for electron–molecule and electron–atom collisions are compared.

Dissociative excitation of the 2 S°, 2 P°, and 2 D° levels of the cobalt atom in collisions of slow electrons with cobalt dibromide molecules

The dissociative excitation of the odd doublet S, P, and D levels of the cobalt atom in collisions of slow electrons with cobalt dibromide molecules was studied experimentally. Eighty six dissociative excitation cross-sections were measured at an exciting electron energy of 100 eV. Two optical excitation functions were recorded at electron energies in the range 0–100 eV. The total dissociative excitation cross-sections were calculated for 20 levels based on the obtained results. The cross-sections of the formation of excited cobalt atoms in e–Co, e–CoBr2, and e–CoCl2 collisions were compared.

Low-energy collisions between electrons and [formula omitted]: Cross sections and rate coefficients for all the vibrational states of the ion

We provide cross sections and Maxwell rate coefficients for reactive collisions of slow electrons with BeH+ ions on all the eighteen vibrational levels (X1Σ+,vi+=0,1,2,…,17) using a Multichannel Quantum Defect Theory (MQDT)—type approach. These data on dissociative recombination, vibrational excitation and vibrational de-excitation are relevant for magnetic confinement fusion edge plasma modeling and spectroscopy, in devices with beryllium based main chamber materials, such as the International Thermonuclear Experimental Reactor (ITER) and the Joint European Torus (JET). Our results are presented in graphical form and as fitted analytical functions, the parameters of which are organized in tables.

TlII excitation cross-sections in collisions of slow electrons with thallium atoms

Excitation of a singly-charged thallium ion in electron collisions with thallium atoms has been studied experimentally. Seventy excitation cross sections have been measured at an exciting electron energy of 30 eV. Ten optical excitation functions (OEFs) have been recorded in the incident electron energy range of 0–200 eV. For seven TlII spectral series, the dependence of excitation cross-sections on the principal quantum numbers of upper levels has been studied. A comparison of findings with data from preceding publications is presented.

Excitation of Lanthanum and Lutetium Double-Charged Ions in Electron-Atom Collisions

Excitation of LaIII and LuIII in collisions of slow electrons with La and Lu atoms (excitation with simultaneous double ionization) have been studied in experiment. At exciting electron energy of 50 eV at 19 excitation cross-sections for each of LaIII and LuIII were measured. At two optical excitation functions for both of ions were recorded, in the electron energy range of 0–200 eV for LaIII and in the range of 0–250 eV for LuIII. Absolute values of excitation cross-sections for similar levels of LaIII and LuIII are compared.

Excitation of GeII in collisions of slow electrons with germanium atoms

Inelastic collisions of slow electrons with germanium atoms leading to the population of excited levels of a singly charged germanium ion have been studied experimentally. One hundred GeII excitation cross sections have been measured at an exciting electron energy of 30 eV. Nine optical excitation functions (OEFs) have been recorded in the electron energy range of 0–200 eV. The behavior of excitation cross-sections is discussed for six GeII spectral series.

The Franck-Hertz Experiments, 1911–1914 Experimentalists in Search of a Theory

In 1911, James Franck and Gustav Hertz began a collaboration to investigate the nature of collisions of slow electrons with gas molecules that led to a series of carefully planned and executed experiments, culminating in their discovery of inelastic collisions of electrons with mercury vapor atoms in 1914. This paper tells the story of their collaboration and the eventual reinterpretation of their results as a confirmation of Niels Bohr’s new atomic theory, largely as a result of experiments done in North America during the Great War.

Dissociative excitation of even levels of the singly charged yttrium ion in collisions of slow electrons with yttrium tribromide molecules

The method of extended crossing beams in conjunction with optical spectroscopy is used to study the dissociative excitation of even levels of YII in e-YBr3 collisions. At the exciting electron energy of 100 eV, 38 dissociative excitation cross sections are measured. Comparison of these cross sections with the cross sections for direct excitation in e-Y collisions shows that, for all the investigated even levels of YII, dissociative excitation is more efficient than direct one.

Dissociative excitation of even triplet and quintet levels of the iron atom in collisions of electrons with iron diiodide molecules

The method of extended crossing beams is used to study inelastic collisions of slow electrons with iron dichloride molecules. The dissociative excitation of even triplet and quintet levels of the iron atom at the incident electron energy of 100 eV is examined. The resulting dissociative excitation cross sections are compared to the cross sections of the excitation of FeI in electron-atom collisions.

Vibrationally inelastic collisions of slow electrons with polyatomic molecules

We present a computational method developed for calculations of vibrationally inelastic collisions of electrons with polyatomic molecules. The method is first applied to calculate vibrational excitations of cyclopropane molecule. In second step we demonstrate how the method can be altered for collisions at higher energies, namely 50-300 eV. In the case of furan molecule we compare a size of summed vibrationally inelastic cross sections with the elastic data. For the two molecules studied we also compare our calculated results with the available experimental data.

Vibrationally inelastic collisions of slow electrons with cyclopropane and diacetylene

This is a joint experimental and theoretical study bringing new results on vibrationally inelastic electron scattering by cyclopropane and diacetylene.

Formation of excited singly charged barium ions in collisions of slow electrons with barium dibromide molecules

The method of extended crossing beams is used to study inelastic collisions of slow electrons with barium dibromide molecules. The resulting optical emission spectrum contains only the spectral lines of the singly charged barium ion. At an exciting electron energy of 100 eV, the cross sections of dissociative excitation for nine spectral lines of BaII are measured; for all these lines, the optical excitation functions over an electron energy range of 0 to 100 eV are recorded. The possible channels of the dissociative excitation of BaII are discussed.

Dissociative excitation of doublet and octet levels of the manganese atom in collisions of electrons with manganese diiodide molecules

The dissociative excitation of doublet and octet levels of the manganese atom in collisions of slow electrons with manganese diiodide molecules is studied. At the exciting electron energy of 100 eV, the excitation cross sections for 28 and 12 transitions, respectively, from doublet and octet states of manganese atom are measured. In the exciting electron energy range of 0–100 eV, six optical excitation functions are recorded. The possible channels of the formation of excited manganese atoms at low electron energies are discussed.

Excitation of singlet levels of a singly charged scandium ion in e-Sc collisions

The excitation of singlet levels of the singly charged scandium ion is experimentally studied in collisions of slow electrons with scandium atoms. At the exciting electron energy of 30 eV, 59 excitation cross sections are measured. In the electron energy range of 0–200 eV, seven optical excitation functions are recorded. On the basis of these data the total excitation cross sections are calculated for 11 even and 9 odd levels of Sc II, as well as the contribution of cascade population to 8 even and 7 odd levels.

Low-energy electron elastic scattering from Mn, Cu, Zn, Ni, Ag, and Cd atoms

Electron elastic total cross sections (TCSs) for ground and excited Mn, Cu, Zn, Ni, Ag, and Cd atoms have been investigated in the electron-impact energy range 0 \ensuremath{\leqslant} $E$ \ensuremath{\leqslant} 1 eV. The near-threshold TCSs for both the ground and excited states of these atoms are found to be characterized by Ramsauer-Townsend minima, shape resonances, and extremely sharp resonances corresponding to the formation of stable bound negative ions. The recently developed Regge-pole methodology where the crucial electron-electron correlations are embedded is employed for the calculations. From close scrutiny of the imaginary parts of the complex angular momenta, we conclude that these atoms form stable weakly bound ground and excited negative ions as Regge resonances through slow electron collisions. The extracted electron binding energies from the elastic TCSs of these atoms are contrasted with the available experimental and theoretical values.

The dissociative excitation of singlet levels of the singly charged lanthanum ion in collisions of electrons with lanthanum bromide molecules

The method of extended crossing beams was used to study inelastic collisions of slow electrons with LaBr3 molecules. Dissociative excitation caused the appearance of spectral lines of the singly charged lanthanum ion. 38 dissociative excitation cross sections of LaII spectral lines (upper singlet levels) were studied at a 100 eV exciting electron energy. Three optical excitation functions were recorded over the electron energy range 0–100 eV. The cross sections obtained are compared with the data on dissociative excitation cross sections of the LaCl3 molecule.

Dissociative excitation of odd quintet levels of the iron atom by collisions of electrons with iron dichloride molecules

The dissociative excitation of odd quintet levels of the iron atom by collisions of slow electrons with iron dichloride molecules was studied using the method of extended crossing beams. Fifty-five dissociative excitation cross sections were measured at an excitation electron energy of 100 eV. Five optical excitation functions were recorded over an electron energy range from 0 to 100 eV. Some tendencies in the behavior of dissociative excitation cross sections were discussed.