Dissociative excitation of the fluoromethanes by electron impact

Emission spectra following electron impact on molecules of the homologous series of fluoromethanes CH_xF_4-x with x=0-4 have been investigated from the near infrared at 700 nm to the ultraviolet VUV-spectral region at 100 nm. Earlier experimental data for the visible and ultraviolet spectral region were revised and evaluated again on the basis of reliable new data for the dynamic viscosity of the molecules. The measurement of absolute and relative cross-sections were systematically extended into the VUV region from 100 nm to 200 nm. The examination of atomic lines as well as molecular band systems in the VUV gives further insight into the dissociation mechanism and shows that many excited levels even of atomic and molecular species cannot be populated directly, but only by transitions from higher-lying energy levels. Simple steric effects can be distinguished from more complex transition phenomena. Received: 25 February 1998 / Revised: 29 May 1998 and 18 June 1998 / Accepted: 23 June 1998     

Calibration of electron spectra

Energy calibration procedures, which have been used in ESCA, are reviewed. Binding energies of calibration lines suitable for solid and for gaseous samples have been determined. Charging effects of nonconducting samples have been investigated for different X-radiation, sample thickness and material. A calibration relative to lines from some insulating standard compound mixed into the sample was shown to be unreliable, while experiments indicated that in calibrating relative to a surface layer, the carbon line from the hydrocarbon contamination layer can be used as well as a line from a thick layer of a noble metal on a part of the sample.     

Electronic spectra of aliphatic carbonyl compounds by electron impact spectroscopy: II. Saturated ketones

Electron impact energy loss spectra of acetone, 2-butanone, methyl isobutyl ketone, methyl isopropyl ketone, and methyl tertiarybutyl ketone have been recorded at an impact energy of 100 eV and a scattering angle of two degrees. Rydberg assignments have been made using quantum defects and term values obtained by reference to ionization potentials measured by photoelectron spectroscopy. Substituent effects on Rydberg orbital energies are discussed using Taft σ* values.     

Electronic spectra of aliphatic carbonyl compounds by electron impact spectroscopy: III. Unsaturated compounds

Electron impact energy loss spectra at an impact energy of 100 eV and a scattering angle of 2 degrees are presented for propenal (CH₂ = CHCHO) and methyl vinyl ketone (CH₂ = CHCOCH₃). The spectra are tentatively assigned using quantum defects and term values derived from ionization potentials measured by photoelectron spectroscopy. The duality of Rydberg and valence transition assignments in propenal is discussed. It is shown that a transition earlier assigned by Walsh to be π → π* is most probably a Rydberg transition.     

Electronic spectra of aliphatic carbonyl compounds by electron impact spectroscopy: I. Saturated aldehydes

The electron impact energy loss spectra of acetaldehyde, propionaldehyde and isobutyraldehyde have been studied at an impact energy of 100 eV and a scattering angle of two degrees. Transitions are tentatively assigned on the basis of term values calculated with respect to ionization potentials determined by photoelectron spectroscopy. Substituent effects on Rydberg orbital energies are discussed using Taft σ* values.     

The threshold electron impact spectrum of molecular oxygen

The threshold electron impact spectrum of molecular oxygen has been studied using a high energy resolution electron spectrometer in the energy region 2-15.2 eV and the penetrating field method for scattered electrons. The measured features such as core excited resonances as well as Rydberg and valence states are measured in threshold and metastable spectra. They are identified and assigned according to their energy positions, energy spacing between vibrational levels and compared with similar data from the literature. A good agreement was found in the energy positions between measured features and corresponding potential energy diagram for Rydberg states for molecular oxygen given by Morrill et al. [1].Received: 13 January 2004, Published online: 20 April 2004PACS: 34.80.Gs Molecular excitation and ionization by electron impact     

Backscattered electron spectra from graphite

The backscattered electron spectra from graphite sample were studied both experimentally and theoretically at impact energies between 500 and 5000 eV. The angle of the incident electron beam was 50° and the detection angle was 0° with respect to the surface normal, respectively. Monte Carlo (MC) simulations were performed based on the Classical Transport Theory (CTT) model to mimic the experimental spectra. In our simulations, both elastic and inelastic scattering of primary electrons and secondary electron emission from graphite are taken into account. There is found satisfactory agreement between measured and calculated electron spectra.     

The conversion electron spectra of Lu169 and Lu170

The isotopes Lu¹⁶⁹ and Lu¹⁷⁰, obtained in the fraction of radioactive Lu isotopes by bombarding a Ta target with fast protons, were measured on a double focusing -ray spectrometer. The gamma transitions are given together with the relative intensities of the conversion lines. The multipolarity of the transition is determined for some gamma transitions from the internal conversion coefficient ratios of theK andL shells.

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Lu¹⁶⁹ Lu¹⁷⁰

Lu¹⁶⁹ Lu¹⁷⁰, . - . - K L .

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We should like to thank V. Kopiva and M. Buriánek for help during the measurements.     

Relative line intensities in the argon L x-ray emission spectra produced by 0.3 to 3 keV electron impact

This note presents the first measurement of the relative intensities of the radiative processes of the L shell of argon. The partial emission cross sections are deduced. Our data show that the radiative transitions within the excited ion are very sensitive to the incident electron energy.     

The influence of electron scattering on the lineshape of auger and photoelectron spectra

A simplified model of Auger and photoelectron scattering in solids is presented. Within the framework of the model the relation between the distribution of backscattered primary electrons and Auger photoelectron distribution is obtained in terms of the geometric factor and the density of inelastic electron scattering probability. The new algorithm of spectrum background subtraction is formulated and applied to process the X-ray photoelectron and Auger spectra for a series of oxygen, fluorine, and copper compounds. It is shown that the method accuracy for the peak area measurements is better than 10%.     

α粒子激励下氩激发态光谱

用自制的单光子计数系统,测定了氩在α粒子激励下的发射光谱.在 300～600 nm范围,认证得到4条 Arl,24条 ArⅡ1条ArⅢ谱线.实验研究了谱线强度随气体压强的变化规律.经初步统计分析,提出在472.8 nm,487.9nm等谱线上实现核泵浦激光振荡的可能性.     

The electron spin resonance spectra of the toluene,p-xylene and m-xylene anions

The electron spin resonance (e.s.r.) spectra of the anions of toluene, p-xylene and m-xylene have been studied and the proton hyperfine coupling constants determined. These are in excellent agreement with the predictions of Hückel molecular orbital theory.     

The threshold electron impact spectrum of H2O

The threshold electron spectrum of H2 O was obtained using a high resolution electron impact spectrometer combined with the penetrating field method for scattered electrons with energies close to zero eV. The valence, triplet Rydberg states, as well as the resonances were identified and are discussed in the energy region 5.2–14.3 eV. The threshold spectrum confirms the influence of resonances on the enhancement of the intensity of some Rydberg states above 10 eV. The vibrational spacing of the observed transitions of the Rydberg states indicates that the water molecule is excited in the symmetric stretching mode.     

Hyperconjugation in the electron resonance spectra of free radicals

The electron resonance hyperfine splitting a _H produced by protons of a methyl group attached to one of the aromatic carbon atoms of a π-electron radical is calculated by the valence bond theory, treating the exchange inter-action between the odd electron and the methyl group as a perturbation. The formula a _H = Q _ρ which relates a _H for a ring proton with the spin density ρ on the aromatic carbon atom also holds for methyl protons. Q is predicted to be positive with a theoretical value of about 28 gauss in the ethyl radical. Experimental data for several radicals indicate that Q is about 25 gauss. It is suggested that the CH₃ and CH₂ protons appear to be equivalent in the spectrunl of the ethyl radical because Q has the same magnitude for both. The spectra of some Wurster's blue ions are interpreted on the assumption that hyperconjugation takes place between methyl groups and the nitrogen atoms.     

The use of electron loss data as unit impulse response function in deconvolution of electron spectra

A simple model is presented to investigate whether the electron backscatter spectrum measured at the energy of an Auger peak provides an adequate respo     

Linewidth inversion in electron resonance spectra

The electron resonance spectrum of the cation of vanadyl octaethylporphyrin exhibits an unusual linewidth variation with the outer spectral lines sharper than the inner components. This observation corresponds to an inversion of the line broadening normally observed for vanadium (IV) complexes. The linewidth inversion is found to result from the anisotropy in the vanadium hyperfine interaction and the zero-field splitting which, when coupled with the molecular rotation, provides a powerful relaxation process. It is possible to provide a quantitative account of the observed linewidth variation if the anisotropy in the g tensor for the electron on vanadium is also included in the theory.     

The electron structure and x-ray emission spectra of noble metal aluminides

A calculation of the electron structure of [Al₈Cu₄] and [Al₈Au₆]- clusters was performed by the XαSW SCF-method. The X-ray emission and photoelectron spectra for noble metal aluminides Al₂Cu and Al₂Au are interpreted on the base of these calculations. The question of the possible influence of d-states on the distribution of Al3s-states and the shape of the AlL_2,3-emission spectrum is discussed for Al₂Cu.