Laser-assisted (e, 2e) collisions in helium

The influence of a strong laser field on the dynamics of fast (e, 2e) collisions in helium is analyzed in the asymmetric, coplanar geometry. The interaction of the laser field with the incident, scattered and ejected electrons is treated in a non-perturbative way, while the remaining interactions are treated by using first order perturbation theory. Detailed calculations are performed for an incident electron energyE _{k i}=600 eV, an ejected electron energyE _{k B}=5 eV and a scattering angle θ _A =4°. The influence of the laser parameters (photon energy, intensity and direction of polarization) on the angular distribution of the ejected electron is analyzed. We find that in general the triple differential cross sections are strongly dependent on the dressing of the projectile and the target by the laser field.     

Relativistic (e, 2e) collisions on atomic inner shells in symmetric geometry

We report here on an (e, 2e) experiment at relativistic electron energies (E ₀=300 keV and 500 keV) in coplanar symmetric geometry. Absolute triple differential cross section measurements forK-shell ionisation of gold, silver and copper are compared with a number of simple first order approximations. Appreciable discrepancies between theory and experiment are found, which reduce with decreasingZ and increasing primary energy. The theoretical calculations show that spin flip effects are important in symmetric geometry, in earlier works these had been neglected.     

Electron spectroscopy of hydrogen fluoride resonances

Transmission electron spectroscopy has been applied to determine the energies of resonances in HF. In addition to a sharp resonance at 10.05 eV, a resonance series exhibiting both vibrational and rotational structure is resolved in the energy range between 12 eV and 13 eV and the following molecular constants are obtained: B = 20.4 cm^?1, r_e, = 0.93 Å, ω_e 0.132 eV, ω_ex_e = 0.006 eV and D_e = 0.73 eV. The resonance spectrum is analysed with reference to an electron energy loss spectrum and approximate potential energy curves are deduced. Serious discrepancies are found between the present results and the data reported by Spence and Noguchi.     

Angular distributions of electrons in the (e, 3e) reaction

The differential cross sections for the Kr (e, 3e) Kr⁺⁺ reaction are calculated (by using correlated wave function) in the case of high incident energy (5 keV) for the three terms of the final Kr⁺⁺ (4p ⁴) ion. We have performed an ab initio calculation on the basis of the first Born approximation using correlated wave functions for the target. The agreement with the first available (e, 3e) experimental data is fairly good. Other typical experimental situations are proposed and discussed.     

Introduction of the shell structure into the Thomas—Fermi energy density functional for neutral atoms

The Thomas—Fermi energy density functional is constructed for the Na atom using H-like wavefunctions. Minimization of the functional with respect to the Z in the wavefunctions leads to the energy value ot ?166.35 e_O²/a_O, which compares favorably with the Hartree—Fock value of ?161.8 e_O²/a_O.     

The ground-state potential energy function of PO+

The ground-state potential energy function of PO⁺ has been calculated from the set of molecular constants B _e, ω_e, a _i (i = 1, … , 5), R _e, D _e and C₄ in the form of generalized potential energy function previously suggested by us for solving the inverse spectroscopic problem.     

Electrochemical oxidation of 9-methylxanthine

The electrochemical oxidation of 9-methylxanthine proceeds via four voltammetric oxidation peaks at the pyrolytic graphite electrode. The first voltammetric oxidation peak (peak I_a) is a 1e reaction giving a radical which dimerizes to 8,8′-bi-9-methyl-9H-purine-2,6-(1H, 3H)-dione. Peak II_a is a further 2e electrooxidation of the peak I_a dimer to another yellow dimer 8,8′-bi-9-methyl-9H-purine-2,6-(1H)-dione-3,5-(3H)-diiminylidene. This dimer is not very stable and it hydrolyzes to 1-methyl allantoin. Peak III_a is an adsorption pre-peak to peak IV_a which corresponds, overall, to a direct 4e?4H⁺ electrooxidation of 9-methylxanthine to an unstable diimine of 9-methyluric acid. Hydrolysis of this diimine leads to a variety of ultimate products.     

Energy shift in (dtμ)e due to the finite size of the muonic molecular ion (dtμ)+

The energy shift due to the presence of the extended (dtμ)₁₁ pseudonucleus (in its first excited state with one unit of angular momentum) in the quasihydrogenlike system (dtμ)₁₁ e _1s is estimated using perturbation theory up to second order with two choices of zeroth order electron wavefunctions. The energy shift is found to be 0.50 meV using pure Coulomb electron wavefunctions and 0.58 meV using electron wavefunctions calculated with a potential modified to take partial account of the finite size of (dtμ)₁₁. In both cases, the perturbation Hamiltonian is expanded in multipoles, retaining terms up to and including octupole terms.     

A simple analytical approximation for the potential energy of diatomics

A correlation between the Dunham expansion coefficients, a₂ ≈ 0.64 a₁², is found which holds for diatomics for different types. Based on this correlation, a four-parameter power approximation using ω_e, B_e, α_e and D_e is suggested which reproduces the ground-state potential curves for diatomics within 2%.     

Ab initio investigation of 2,2′‐bis(4‐trifluoromethylphenyl)‐5,5′‐bithiazole for the design of efficient organic field‐effect transistors

The initial molecular structure of 2,2′‐bis(4‐trifluoromethylphenyl)‐ 5,5′‐bithiazole has been optimized in the ground state using density functional theory (DFT). The distribution patterns of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) have also been evaluated. To shed light on the charge transfer properties, we have calculated the reorganization energy of electron λ_e, the reorganization energy of hole λ_h, adiabatic electron affinity (EA_a), vertical electron affinity (EA_v), adiabatic ionization potential (IP_a), and vertical ionization potential (IP_v) using DFT. Based on the evaluation of hole reorganization energy, λ_h, and electron reorganization energy, λ_e, it has been predicted that 2,2′‐bis(4‐trifluoromethylphenyl)‐5,5′‐bithiazole would be a better electron transport material. Finally, the effect of electric field on the HOMO, LUMO, and HOMO–LUMO gap were observed to check its suitability for the use as a conducting channel in organic field‐effect transistors. © 2015 Wiley Periodicals, Inc.     

The absorption spectrum of carbon monoxide in the CO(3Π r,a) state between 215 nm and 285 nm

Bye-beam excitation of a He/CO mixture the CO(³Π _r ,a) state was sufficiently populated to allow the measurement of the absorption spectrum. The (0, 0), (1, 1), (2, 2) and (0, 1) bands of thec ³Π←a ³Π system of CO have been observed and the molecular constantsT _e =92036.0 cm^?1 (for the band head), ω _e =2249.5 cm^?1, ω _e x _e =29.5 cm^?1 have been derived for CO(c). A new electronic state withT _e =91854.3 cm^?1, ω _e =848.4 cm^?1, ω _e x _e =9.8 cm^?1,B _e =1.351 cm^?1, and α _e =0.021 cm^?1 was identified to be a³Σ state. It seems to be very likely that this state is the CO (3pσ,³Σ,j) state discussed in the literature. The results indicate a perturbation of the υ=1 levels of the new state by the CO (c,υ=0) levels. Another strong perturbation is found in the υ=4 levels. The three CO(³Σ,b,υ′=0,1,2)←CO (a,υ″=0) bands were also investigated yielding for CO(b):T _e =83778 cm^?1, ω _e =2335 cm^?1, ω _e x _e =59 cm^?1 andB _e =1.86 cm^?1.     

Synthesis of polyoxygenated dibenzo[a,e]cycloheptatrienes

A successive route for the synthesis of substituted dibenzo[a,e]cycloheptatriene 1 was established by the reduction of 2-allylbenzaldehyde 4, the BF₃·OEt₂-mediated intermolecular coupling of 2-allylphenylmethanol 5 with oxygenated benzenes 6, the olefinic oxidative cleavage of 7 and the intramolecular ring-closure of 8. Functionalized anthracene 13 were prepared from 2-vinylbenzaldehyde 9. The key structures were confirmed by X-ray single crystal diffraction analysis.     

A simple chemical model for the electron polarization of cyclopentyl radicals produced in radiolysis

The electron polarization of cyclopentyl radicals was observed by Smaller . This paper presents an attempt to account for this observation by an initial polarization mechanism. The mechanism is based on the addition of hydrogen atoms to the product olefin to give the alkyl radicals. The electron polarization of the alkyl radicals arises from the polarized hydrogen atoms. It should be emphasized that the processes leading to polarized H atoms are not established but it is assumed that they are formed initially with the populations in αa_eα_N and α_eβ_N being greater than β_eα_N and β_eβ_N, respectively.     

Tetragonal distortions and vibronic coupling in hexaflouro nickel(II) and copper (II) complexes

Two parameters, axial (R_a) and equatorial (R_e) metal-ligand distances, describe the tetragonal distortions of the NiF^4?₆ and CuF^4?₆ complexes under study. The experimental values of R_a plotted vs R_e exhibit a smooth curve type dependence valid for MF₆ chromophore of solid state compounds. In the model study it becomes explained by analyzing the shape of the adiabatic potential surface (APS) of the form of E_T(R_a, R_e). Around the energy minima the map of numerical values (obtained by the quantum-chemical CNDOUHF and INDOUHF methods) was transformed to an analytic form from which the quantitative characteristics of APS were obtained in a new, simple way. The set of equatorial-axial parameters as well as the set of vibronic parameters were evaluated and discussed in more detail.     

Nonequilibrium vibrational populations and dissociation rates of oxygen in electrical discharges

Nonequilibrium vibrational distributions and dissociation rates of molecular oxygen in both electrical and thermal conditions have been calculated by solving a system of master equations including V-V (vibration-vibration), V-T (vibration-translation) and e-V (electron-vibration) energy exchanges. The dissociation constant under thermal conditions (i.e. without electrons) follows an Arrhenius law with an activation energy of 120 kcal/mole, while the corresponding rates under electrical conditions (5000 ? T_e ? 15000 K, 300 ? T_g ? 1000 K, 10¹¹ ? n_e ? 10¹² cm^?3,5 ? p ? 20 torr) increase with decreasing gas (T_g) and electron (T_e) temperatures and pressure (p) and with increasing electron density (n_e). These results are explained on the basis of the different interplay of V-V and V-T energy exchanges and are rationalized by means of simplified models proposed in the literature. The accuracy of the present results is discussed paying particular attention to the dependence of V-V and V-T rate coefficients on the vibrational quantum number. A comparison of the calculated dissociation rates with the corresponding ones obtained by the direct electron impact mechanism shows that the present mechanism prevails at low electron and gas temperatures. Finally a comparison is shown between theoretical and experimental dissociation rates under electrical and thermal conditions.     

A simple method for non-parametric estimation of the probability distribution function of diatomic molecules by electron diffraction

Treating the Debye intensity relationship as a linear Fredholm integral equation of the first kind, a method is developed for a non-parametric estimation of the probability distribution function P/r) for diatomic molecules from electron-diffraction data. Since the problem is an ill-posed one, Tikhonov's regularization procedure was used for the solution. The method was applied to iodine for which the non-parametric P/r) function is obtained. Based on this function the electron-diffraction parameters r_g, r_a and l_a are estimated by the linear least-squares method without a priori assumptions about the form of the vibrational potential. Approximating the potential by the Dunham expansion, the parameters r_e, ω_e, K₃ and K₄ are also estimated. The results are compared with those obtained from conventional analytical representation of an intensity function. Comparison is also made with spectroscopic data for iodine.     

Carbon-13 NMR spectra of some chlorins and other chlorophyll degradation products

The ¹³C NMR spectra of the methyl esters of phaeophorbides-a and -b, mesophaeophorbides-a and -b, pyrophaeophorbide-a, mesopyrophaeophorbide-a, chlorin-e₆, mesochlorin-e₆, chlorin-p₆, rhodin-g₇, mesorhodin-g₇, phaeoporphyrin-a₅, 2-vinylphaeoporphyrin-a₅, rhodoporphyrin-XV, and 2-vinylrhodoporphyrin-XV, and of trans-octaethylchlorin, in deuteriochloroform and/or trifluoroacetic acid solution are reported. On the basis of comparisons within this comprehensive series and proton off-resonance decoupled spectra, assignments of most resonances are made; complete assignment of the quaternary “pyrrole” ring carbons was difficult to accomplish. A downfield shift of the α- and β-meso-carbons of chlorins in trifluoroacetic acid relative to deuteriochloroform is used to confirm that the Chlorobium chlorophylls (660) from Chloropseudomonas ethylicum are meso-methylated at the δ-position.     

On the existence of arbitrary four-body (or quasi-four-body) molecules

At wavelengths near 1 mm three rotational transitions of²⁰⁵Tl¹⁹F and²⁰³Tl¹⁹F have been observed. The analysis including previous measurements on rotational transitions at larger wavelengths resulted in sets of the Dunham coefficientsY ₀₁,Y ₁₁,Y ₂₁,Y ₃₁,Y ₀₂,Y ₁₂, andY ₀₃ of the two isotopic species. With these microwave data the constantsY ₁₀ ≈ ω _e and ?Y ₂₀ ≈ ω_e x_e were determined. The parameters of the Dunham potentiala ₀,a ₁,a ₂,a ₃,B _e andr _e are given. The Dunham coefficientsY _mn with the smallest relative experimental error show deviations from the general mass relations between isotopic species indicating a violation of the Born-Oppenheimer approximation.