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     

Total cross sections for electron scattering from fluoromethanes: A revised additivity rule method

The additivity rule for electron-molecule scattering is revised by considering the difference between the free atom and the bound atom in the molecule.The total cross sections for electron scattering from fluoromethanes(CF4,CF3H,CF2H2,and CFH3) are calculated in an energy range from 100 eV to 1500 eV by the revised additivity rule.The present calculations are compared with the original additivity rule results and the available experimental data.Better agreement with each other is obtained.     

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: 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.     

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.     

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.     

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     

Magnetoplasma spectra of two-dimensional electron rings

A hydrodynamical approach is employed to study the collective excitations of a two-dimensional electron gas confined in a ring geometry, under a normal magnetic held. The theory predicts a rich spectrum of magnetoplasma excitations, with several branches of high- and low-frequency resonances. It is shown that the low-frequency resonances can be identified as edge magnetoplasmons localized at the inner and outer boundaries of the ring, exhibiting their characteristic antidot-like and dot-like features. The high-frequency resonances are essentially bulk two-dimensional magnetoplasmons. Our calculated magnetoplasma modes and their associated induced charge densities and dipole moments are compared with a recent experiment, and it is found that most of the experimentally observed features of the spectrum are accounted for with the present theory.     

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%.     

10-25 keV电子致厚W,Au靶韧致辐射谱的测量

测量了10-25 keV电子碰撞厚W, Au靶产生的韧致辐射谱, 并与Monte Carlo程序PENELOPE模拟的X射线谱进行了比较, 除在3 keV前实验谱略低于理论谱外, 整体上两者符合得很好. 在模拟电子与靶材料相互作用产生韧致辐射时, PENELOPE程序中只包含有普通韧制辐射的截面数据. 我们的实验结果表明, 在电子与固体靶相互作用时, 没有明显的极化韧致辐射产生, PENELOPE程序能够可靠地描述电子与固体厚靶相互作用产生的韧致辐射.     

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.     

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 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     

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.