Hoshino Masamitsu

The central (Nc) and terminal (Nt) nitrogen K-shell photoelectron spectra (PESs) of N2O molecules have been measured in the σ shape resonance energy region at temperatures of ∼300 and ∼630 K. Estimating vibrational populations based on the Boltzmann distribution at these temperatures, PESs of vibrationally ground and bending-excited levels in the initial electronic ground state were extracted. Vibrationally integrated partial cross sections and asymmetry parameters for ionization from vibrationally ground and bending-excited levels were obtained as a function of the incident photon energy by integrating PESs over the vibrational levels of the core-hole states. In Nc photoionization, the shape resonance from the bending-excited level was found to be shifted to the lower photon energy side and to become narrower than that from the ground vibrational level. In Nt photoionization from the bending-excited level, the downward shift of the resonance is more significant than that in Nc ionization. These experimental findings are qualitatively consistent with theoretical predictions and suggest that the shape resonance associated with the Nt core hole is more sensitive to the bending angle of the initial state than is the shape resonance associated with the Nc core hole. The asymmetry parameters for photoionization from the bending-excited level, however, showed almost the same behavior as those from the ground vibrational level for both K-shell photoionization channels and in the photon energy range studied here.

As a sequel paper to our study of the elastic scattering for electron collisions with phosphorus trifluoride, PF3 molecules, we report absolute inelastic differential and integral cross sections (DCS and ICS) of vibrational excitations for the compound fundamental vibrational modes v13 (v1 + v3), v24 (v2 + v4), and their sum in the impact energy range of 2.0-10 eV and over a scattering angle range of 20°-130°. The measured angular distributions of scattered electron intensities for the present inelastic scattering are normalized to the elastic peak intensity corresponding to the DCSs of He. These vibrational excitation measurements demonstrate the presence of resonances around 2 eV and also around 6-10 eV. In addition, a generalized oscillator strength analysis is applied to derive oscillator strength f0-values and (unscaled Born) ICSs from the corresponding DCSs measured for the low-lying optically allowed 8a1 -1 → 7e (σ∗) excitation band, which is assigned as the Jahn-Teller splitting and 8a1 -1 → 4s Rydberg transition at impact energies of 100, 200, and 300 eV, over a scattering angle range of 1.0°-15°. The f0-values obtained in the present study are compared with the results of previous photoabsorption and pseudo-optical measurements. The unscaled Born ICSs are compared with the binary-encounter f-scaled Born ICSs estimated over a wide impact energy region from the excitation thresholds.

We report absolute elastic differential cross sections (DCSs) for electron collisions with phosphorus trifluoride, PF3, molecules (e(-) + PF3) in the impact energy range of 2.0-200 eV and over a scattering angle range of 10 degrees-150 degrees. Measured angular distributions of scattered electron intensities were normalized by reference to the elastic DCSs of He. Corresponding integral and momentum-transfer cross sections were derived by extrapolating the angular range from 0 degrees to 180 degrees with the help of a modified phase-shift analysis. In addition, due to the large dipole moment of the considered molecule, the dipole-Born correction for the forward scattering angles has also been applied. As a part of this study, independent atom model calculations in combination with screening corrected additivity rule were also performed for elastic and inelastic (electronic excitation plus ionization) scattering using a complex optical potential method. Rotational excitation cross sections have been estimated with a dipole-Born approximation procedure. Vibrational excitations are not considered in this calculation. Theoretical data, at the differential and integral levels, were found to reasonably agree with the present experimental results. Furthermore, we explore the systematics of the elastic DCSs for the four-atomic trifluoride molecules of XF3 (X = B, N, and P) and central P-atom in PF3, showing that, owing to the comparatively small effect of the F-atoms, the present angular distributions of elastic DCSs are essentially dominated by the characteristic of the central P-atom at lower impact energies. Finally, these quantitative results for e(-) - PF3 collisions were compiled together with the previous data available in the literature in order to obtain a cross section dataset for modeling purposes. To comprehensively describe such a considerable amount of data, we proceed by first discussing, in this paper, the vibrationally elastic scattering processes whereas vibrational and electronic excitation shall be the subject of our following paper devoted to inelastic collisions. Published by AIP Publishing.

Synopsis We report measurements on differential cross sections (DCSs) for electron-impact excitation to the optically-allowed b1Πu state in molecular nitrogen in the impact energy range of 20 - 400 eV. Absolute excitation DCSs normalized by the relative flow technique were transformed to generalized oscillator strengths (GOSs) as a function of momentum transfer squared. Integral cross sections (ICSs) for the transitions to the b1Πu state were compared with the BEf-scaled plane-Born ICS as well as previous experimental studies.

Synopsis We report absolute electron elastic scattering differential cross sections (DCSs) from PF3 molecules. The crossed-beam method was used in conjunction with the relative flow technique (using helium as the reference gas) to obtain absolute values. Very good agreement between the experimental DCSs and those calculated with the IAMSCAR method has been found for the higher impact energy (above 50 eV). We have also compared the measured DCSs for PF3 with experimental results for other fluorine compounds, XF3 (X = B, C, N and CH), as well as with those derived from the calculated atomic fluorine cross sections multiplied by a factor of 3.

Absolute grand total cross sections for electron scattering from N-2 are obtained in the energy range from 20 eV down to 5 meV with very narrow electron energy width of 9 meV using the threshold-photoelectron source. Total cross sections obtained in the present study are compared with the previous experimentally obtained results. At the very-low energy region below 50 meV, the present total cross sections are somewhat smaller than those reported by the Aarhus group [S.V. Hoffmann et al., Rev. Sci. Instrum. 73, 4157 (2002)], which has been the only experimental work that provided the total cross sections in the very-low energy region. The energy positions of the peaks in the total cross sections due to the (2)Pi(g) shape resonance are obtained with higher accuracy, due to the improved uncertainty of the energy position in the present measurement compared to the previous works. The resonance structure in the total cross sections due to the Feshbach resonances of N-2 at around 11.5 eV are also observed. Analysis of the resonant structure was carried out in order to determine the values of resonance width of Feshbach resonances of N-2.

Electron energy loss spectra of carbon tetrafluoride, silicon tetrafluoride, and germanium tetrafluoride molecules (CF4, SiF4, and GeF4) have been measured for incident electron energies of 50-360 eV at 1.5 degrees-15.5 degrees and for 30 eV and 30 degrees scattering angle, while sweeping the energy loss over the range 9.0-20.0 eV. Low-lying valence excited triplet and singlet states are investigated by quantum chemical ab initio calculations. The Rydberg series converging to the (lowest) ionisation energy limits of XF4 (X = C, Si, Ge) are also identified and classified using the systematic behaviour according to the magnitude of the quantum defects. A generalized oscillator strength analysis is employed to derive oscillator strength f(0) value and the apparent Born integral cross sections from the corresponding differential cross sections by using the Vriens formula for the optically allowed transitions. The f(0) value is compared with the optical oscillator strength of the photoabsorption, pseudo-photon measurements, and theoretical values. The binary-encounter and f-scaled Born cross sections of the most intense optically allowed transitions have been also derived from the excitation threshold to the high energy region where the Born approximation is valid. Potential energy curves were obtained along the XF3 + F coordinate with two different basis sets to lend support on electron impact dissociation processes yielding radical formation. We found that in CF4, the lowest-lying dissociative character is due to intramolecular conversion from Rydberg 3s to valence character (sigma*(C-F)), whereas in SiF4 and GeF4, an antibonding behaviour prevails. Published by AIP Publishing.

Electron energy loss (EEL) spectra of GeF4 have been measured with incident electrons at 100 eV for 5 degrees scattering angle and at 30 eV for 30 degrees scattering angle, while sweeping the energy loss over the range 7.0-18.0 eV. Low-lying excited triplet, singlet, valence, and Rydberg states are investigated and the assignments supported by quantum chemical ab initio calculations. This provides the first comprehensive investigation of all singlet and triplet excited electronic states of germanium tetrafluoride up to the first ionization energy. The Rydberg series converging to the (lowest) ionization energy limits of GeF4 are also identified according to the magnitude of the quantum defects (5).

Inelastic and superelastic electron-impact vibrational excitation functions of hot carbonyl sulphide COS (and hot CO2) are measured for electron energies from 0.5 to 3.0 eV (1.5 to 6.0 eV) and at a scattering angle of 90 degrees. Based on the vibrational populations and the principle of detailed balance, these excitation functions are decomposed into contributions from state-to-state vibrational transitions involving up to the second bending overtone (030) in the electronically ground state. Both the (2)Pi resonance for COS around 1.2 eV and the (2)Pi(u) resonance for CO2 around 3.8 eV are shifted to lower energies as the initial vibrational state is excited in the bending mode. The width of the resonance hump for COS changes only little as the molecule bends, whereas that of the overall boomerang resonance for CO2 becomes narrower. The angular distribution of the electrons resonantly scattered by hot COS and hot CO2 is also measured. The different shapes depending on the vibrational transitions and gas temperatures are discussed in terms of the symmetry of the vibrational wave functions.

Integral cross sections for optically allowed electronic-state excitations of atoms and molecules by electron impact, by applying scaled plane-wave Born models, are reviewed. Over 40 years ago, Inokuti presented an influential review of charged-particle scattering, based on the theory pioneered by Bethe forty years earlier, which emphasized the importance of reliable cross-section data from low eV energies to high keV energies that are needed in many areas of radiation science with applications to astronomy, plasmas, and medicine. Yet, with a couple of possible exceptions, most computational methods in electron-atom scattering do not, in general, overlap each other's validity range in the region from threshold up to 300 eV and, in particular, in the intermediate region from 30 to 300 eV. This is even more so for electron-molecule scattering. In fact this entire energy range is of great importance and, to bridge the gap between the two regions of low and high energy, scaled plane-wave Born models were developed to provide reliable, comprehensive, and absolute integral cross sections, first for ionization by Kim and Rudd and then extended to optically allowed electronic-state excitation by Kim. These and other scaling models in a broad, general application to electron scattering from atoms and molecules, their theoretical basis, and their results for cross sections along with comparison to experimental measurements are reviewed. Where possible, these data are also compared to results from other computational approaches.

Here, we report elastic differential cross sections (DCSs) for electron scattering from water in the incident energy range of 2-100 eV. Furthermore, we present a complete study on the electronic excitation of the (a) over tilde B-3(1) and (A) over tilde B-1(1) states at electron impact energies of 15, 20, and 30 eV and in the scattering angle range of 10. -130.. Integral cross sections (ICSs) are determined from the DCSs. Measuring elastic DCSs in various experimental conditions confirmed the reproducibility of the data. The present results agree with the data previously obtained from a conventional collimating tube gas source. Ambiguities associated with the unfolding procedure of the electron energy loss (EEL) spectra for the electronic excitations have been reduced by comparison against the EEL spectrum at high electron impact energy and for small scattering angle. The reliability of the extracted DCSs is improved significantly for optically forbidden contributions from the overlap of the (a) over tilde B-3(1) and (A) over tilde B-1(1) electronic states. The BEf-scaling model is also confirmed to produce the integral cross section for the optical allowed transition of the (A) over tilde B-1(1) state in the intermediate electron energy region above 15 eV.

Absolute differential cross sections (DCSs) for electron interaction with BF3 molecules have been measured in the impact energy range of 1.5-200 eV and recorded over a scattering angle range of 15 degrees-150 degrees. These angular distributions have been normalized by reference to the elastic DCSs of the He atom and integrated by employing a modified phase shift analysis procedure to generate integral cross sections (ICSs) and momentum transfer cross sections (MTCSs). The calculations of DCSs and ICSs have been carried out using an independent atom model under the screening corrected additivity rule (IAM-SCAR). The present elastic DCSs have been found to agree well with the results of IAM-SCAR calculation above 20 eV, and also with a recent Schwinger multichannel calculation below 30 eV. Furthermore, in the comparison with the XF3 (X = B, C, N, and CH) molecules, the elastic DCSs reveal a similar angular distribution which are approximately equal in magnitude from 30 to 200 eV. This feature suggests that the elastic scattering is dominated virtually by the 3-outer fluorine atoms surrounding the XF3 molecules. The vibrational DCSs have also been obtained in the energy range of 1.5-15 eV and vibrational analysis based on the angular correlation theory has been carried out to explain the nature of the shape resonances. Limited experiments on vibrational inelastic scattering confirmed the existence of a shape resonance with a peak at 3.8 eV, which is also observed in the vibrational ICS. Finally, the estimated elastic ICSs, MTCSs, as well as total cross sections are compared with the previous cross section data available. (C) 2015 AIP Publishing LLC.

The electronic state spectroscopy of carbonyl sulphide, COS, has been investigated using high resolution vacuum ultraviolet photoabsorption spectroscopy and electron energy loss spectroscopy in the energy range of 4.0-10.8 eV. The spectrum reveals several new features not previously reported in the literature. Vibronic structure has been observed, notably in the low energy absorption dipole forbidden band assigned to the (4 pi <- 3 pi) ((1)Delta <- (1)Sigma(+)) transition, with a new weak transition assigned to ((1)Sigma(-) <- (1)Sigma(+)) reported here for the first time. The absolute optical oscillator strengths are determined for ground state to (1)Sigma(+) and (1)Pi. transitions. Based on our recent measurements of differential cross sections for the optically allowed (spectroscopy and (1)Pi) transitions of COS by electron impact, the optical oscillator strength f(0) value and integral cross sections (ICSs) are derived by applying a generalized oscillator strength analysis. Subsequently, ICSs predicted by the scaling are confirmed down to 60 eV in the intermediate energy region. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of carbonyl sulphide in the upper stratosphere (20-50 km). (C) 2015 AIP Publishing LLC.

Synopsis We report measurements on differential cross sections (DCSs) for electron impact excitation of the low-lying levels, 4s[3/2](1) and 4s'[1/2](1), of the optically- allowed transitions in Ar atom in the electron energy range of 15 - 300 eV. Integral cross sections (ICSs) for these transitions obtained from the measured DCSs are compared with the BEf-scaled Born ICS.

We report absolute differential cross sections (DCSs) and integral cross sections (ICSs) for the electronic excitation to the (a) over tilde B-3(1) and (A) over tilde B-1(1) states as well as the elastic scattering of H2O molecules. The measurements are performed in the scattering angle range of 10 - 130 degrees, and impact energies 15, 20, 30 eV for the electronic excitations and energy range 2.0 - 100 eV for the elastic scattering, respectively.

We report on the measurements of the electron impact electronic excitation cross sections for XF4 (X = C, Si and Ge) molecules at 100 eV, 5 degrees scattering angle and 30 eV, 30 degrees in the electron energy loss range 8.0 - 18 eV. For a target of GeF4 molecule, the optically-forbidden behavior has been observed in the lower electron energy loss range.

Absolute total cross sections for electron scattering from He, Ne, Ar, Kr and Xe at very low electron energies were obtained using the threshold photoelectron source, which employs a combination of the penetrating field technique together with the threshold photoionization of atoms by synchrotron radiation. The total cross sections generally agree well with those obtained in the previous experiments above 100 meV, where several experimental works have been reported. Comparison of the measured cross section for He with that of theoretical ones shows very good agreement at very low energies even below 10 meV. Scattering lengths for the e− - noble gas scatterings determined from the our cross sections using the modified effective range theory (MERT) showed that scattering lengths for He and Ne agree well with the values obtained in the previous experimental and theoretical studies. On the other hand, for heavier noble gas atoms, significant discrepancies were found between the scattering lengths derived from MERT analysis to our total cross sections and those reported in previous studies.

In this contribution we probe BF3 low-lying excited singlet states measured at 100 eV, 2.8 degrees scattering angle and triplet states at 40 eV, 40 degrees scattering angle, while sweeping the energy loss over the range 10.020.0 eV. The electronic state spectroscopy has been investigated and the assignments supported by quantum chemical calculations. This provides the first comprehensive investigation of all singlet and triplet excited electronic states of boron trifluoride up to the first ionization potential. A generalized oscillator strength analysis is employed to derive oscillator strength f(0) value and integral cross sections (ICSs) from the corresponding differential cross sections (DCSs). The f(0) value is compared with the optical oscillator strength (OOS) from photoabsorption, and the unscaled Born ICSs are then compared with relevant energy and binary-encounter and f-scaled Born cross section (BEf-scaling) results determined as a part of this investigation. The lowest n members of the Rydberg series have been assigned as converging to the lowest ionization energy limits of boron trifluoride and classified according to the magnitude of the quantum defects (delta).

We report absolute elastic differential cross sections for electron interactions with the C4F6 isomers, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluoro-2-butyne (2-C4F6), and hexafluorocyclobutene (c-C4F6). The incident electron energy range is 1.5-200 eV, and the scattered electron angular range for the differential measurements varies from 15 degrees to 150 degrees. In all cases the absolute scale of the differential cross section was set using the relative flow technique, with helium as the reference species. Atomic-like behaviour in these scattering systems is shown here for the first time, and is further investigated by comparing the elastic cross sections for the C4F6 isomers with other fluorinated molecules, such as SF6 and CnF6 (n = 2, 3, and 6). We note that for all the six-F containing molecules, the scattering process for electron energies above 30 eV is indistinguishable. Finally, we report results for calculations of elastic differential cross sections for electron scattering from each of these isomers, within an optical potential method and assuming a screened corrected independent atom representation. The level of agreement between these calculations and our measurements is found to be quite remarkable in all cases. (C) 2014 AIP Publishing LLC.

As a part of our efforts to characterize the electron attachment reactions of the group IV tetrahalides, XY4 (X = C, Si, Ge and Y = F, Cl, Br) we here follow up on our previous study on XF4 and report electron attachment to the tetrabromides: CBr4, SiBr4 and GeBr4 in the incident electron energy range from about 0 to 10 eV. The formation of Br-, XBr3-, XBr2- and Br-2(-) is observed from all these compounds, and additionally the molecular anion is observed from SiBr4. The main DEA contributions from CBr4 and GeBr4 are observed through a low lying resonance, which we assign as a T-2 shape resonance associated with a single occupation of the t(2) symmetry LUMO+1 of these molecules. This resonance is also apparent in the ion yield from SiBr4, but there the main contributions are the molecular anion and Br- in a narrow energy range peaking at 0 eV. We attribute these 0 eV contributions to a vibrational Feshbach resonance associated with the a(1) symmetry LUMO. Further resonances are observed, for all the compounds investigated here, in the energy range between 3 and 6 eV. To establish the thermochemical thresholds for the individual channels we have conducted DFT calculations from which we report the threshold values, bond dissociation energies and electron affinities for individual fragments and their neutral precursors. These values are compared to values in the literature where available, and discussed in the context of our experimental results. (C) 2014 Published by Elsevier B.V.

Absolute total cross sections for electron scattering from He and Ne are obtained in the energy range from 20 eV down to below 10 meV with a very narrow electron energy width of 6-8 meV using the threshold-photoelectron source. Total cross sections obtained in the present study generally agree well with those obtained in the previous experiments for both He and Ne above 100 meV, where several experimental works have been reported. Comparison of the present cross sections with the theoretical cross sections which have been regarded as the "standard" cross sections shows very good agreement even at very low energies below 10 meV, which confirms the validity of theoretical cross sections. The scattering lengths for electron scattering from He and Ne are also determined from the present total cross sections using the modified effective range theory. The resonant structures in the total cross sections due to Feshbach resonances of He and Ne are also observed. Analysis of the resonant structure was carried out based on the spin-dependent resonant scattering theory in order to determine the values of natural width of Feshbach resonance of Ne.

Absolute total cross sections for electron scattering from He and Ne at electron energies ranging from 6 meV to 20 eV were obtained with the experimental technique employing the threshold-photoelectron source. The measured total cross sections were compared with previous experimental and theoretical cross sections. © Published under licence by IOP Publishing Ltd.

We present and discuss recent results, both experimental and theoretical (where possible), for electron impact excitation of the 3s[3/2](1) and 3s'[1/2](1) electronic states in neon, elastic electron scattering from the structurally similar molecules benzene, pyrazine, and 1,4-dioxane and excitation of the electronic states of the important bio-molecule analogue alpha-tetrahydrofurfuryl alcohol. While comparison between theoretical and experimental results suggests that benchmarked cross sections for electron scattering from atoms is feasible in the near-term, significant further theoretical development for electron-molecule collisions, particularly in respect to discrete excitation processes, is still required.

The development of a full electrostatic slow positron beam apparatus at the Tokyo University of Science is described. The performance of different types of material as the primary moderator and the energy resolution of the beam are detailed.

A new experimental technique for the total cross section measurements of ultra-low energy electron collisions with atoms and molecules utilizing the synchrotron radiation is presented. The technique employs a combination of the penetrating field technique and the threshold photoionization of rare gas atoms using the synchrotron radiation as an electron source in order to produce a high resolution electron beam at very low energy. Absolute total cross sections for electron scattering from He, Ne, Ar, Kr, and Xe in the energy region from extremely low electron energy to 20 eV are presented.

We present and discuss recent results, both experimental and theoretical (where possible), for electron impact excitation of the 3s[32]1 and 3s′[12]1 electronic states in neon, elastic electron scattering from the structurally similar molecules benzene, pyrazine, and 1,4-dioxane and excitation of the electronic states of the important bio-molecule analogue α-tetrahydrofurfuryl alcohol. While comparison between theoretical and experimental results suggests that benchmarked cross sections for electron scattering from atoms is feasible in the near-term, significant further theoretical development for electron-molecule collisions, particularly in respect to discrete excitation processes, is still required. © 2014 AIP Publishing LLC.

Absolute differential cross sections (DCSs) for electron impact of the two lower-lying 3s[3/2](1) (P-3(0)) and 3s '[1/2](1) (P-1(1)) electronic states in neon (Ne) have been determined for eight incident electron energies in the range 20-300 eV. Comparisons between our results and previous measurements and calculations, where possible, are provided with best agreement being found with the recent large-scale B-spline R-matrix computations [O. Zatsarinny and K. Bartschat, Phys. Rev. A 86, 022717 (2012)]. Based on these DCSs at 100, 200, and 300 eV, a generalised oscillator strength analysis enabled us to determine estimates for the optical oscillator strengths of the 3s[3/2](1) and 3s'[1/2](1) levels. In this case, excellent agreement was found with a range of independent experiments and calculations, giving us some confidence in the validity of our measurement and analysis procedures. Integral cross sections, derived from the present DCSs, were presented graphically and discussed elsewhere [M. Hoshino, H. Murai, H. Kato, Y. Itikawa, M. J. Brunger, and H. Tanaka, Chem. Phys. Lett. 585, 33 (2013)], but are tabulated here for completeness. (C) 2013 AIP Publishing LLC.

We report results on new absolute cross section measurements for electron impact excitation of the two lowest 3s[3/2](1) and 3s'[1/2](1), optically- allowed electronic-state levels in neon. Those measurements were conducted at eight specific energies in the 20-300 eV energy range. The present results, at the integral cross section level, strongly support those from the recent large-scale B-spline R-matrix computations [O. Zatsarinny, K. Bartschat, Phys. Rev. A 86 (2012) 022717], and resolve a serious discrepancy that had existed between earlier experimental results and theory. Some discrepancies in the differential cross sections, at middle and backward angles, are however still noted. (C) 2013 Elsevier B.V. All rights reserved.

This Letter reports on the first measurements of the lowest lying triplet states as studied by electron energy loss spectroscopy for C4F 6 isomers, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluorocyclobutene (c-C4F6) and hexafluoro-2-butyne (2-C4F6). This study has been performed at an incident electron energy of 30 eV, 30, whilst sweeping the energy loss over the range 2.0-15.0 eV. The electronic state spectroscopy has been investigated and the assignments supported by multi-reference quantum chemical calculations. The transition to the steepest electronic excited potential energy curve, is suggested to be dominant for 2-C4F6, due to the large broadening in its energy profile. © 2013 Elsevier B.V. All rights reserved.

Differential, integral, and momentum transfer cross sections have been determined for the elastic scattering of electrons from the molecules CF 3Cl, CF2Cl2, and CFCl3.With the help of a crossed electron beam-molecular beam apparatus using the relative flow technique, the ratios of the elastic differential cross sections (DCSs) of CF3Cl, CF2Cl2, and CFCl3 to those of He were measured in the energy region from 1.5 to 100 eV and at scattering angles in the range 15° to 130°. From those ratios, the absolute DCSs were determined by utilizing the known DCS of He. For CF3Cl and CF2Cl2, at the common energies of measurement, we find generally good agreement with the results from the independent experiments of Mann and Linder J. Phys. B 25, 1621 (1992)10.1088/0953-4075/25/7/030 Mann and Linder J. Phys. B 25, 1633 (1992)10.1088/0953-4075/25/7/031. In addition, as a result of progressively substituting a Cl-atom, undulations in the angular distributions have been found to vary in a largely systematic manner in going from CF4 to CF3Cl to CF2Cl2 to CFCl3 and to CCl4. These observed features suggest that the elastic scattering process is, in an independently additive manner, dominated by the atomic-Cl atoms of the molecules. The present independent atom method calculation typically supports the experimental evidence, within the screened additivity rule formulation, for each species and for energies greater than about 10-20 eV. Integral elastic and momentum transfer cross sections were also derived from the measured DCSs, and are compared to the other available theoretical and experimental results. The elastic integral cross sections are also evaluated as a part of their contribution to the total cross section. © 2013 AIP Publishing LLC.

Dissociative electron attachment (DEA) to the group IV tetrafluorides: CF4, SiF4 and GeF4, is reported in the incident electron energy range from about 0 to 14 eV. The F-2(-) formation from CF4 is established and the appearance energies (AEs) for F-, CF3- and F-2(-) are determined using a three-point calibration for the energy scale. These are found to be 4.7 +/- 0.1 eV, 4.5 +/- 0.1 eV and 5.6 +/- 0.1 eV, respectively. For SiF4 the AEs for F-, SiF3- and F-2(-), through the dominating resonance are found to be 10.2 +/- 0.1 eV, 10.2 +/- 0.1 eV and 10.3 +/- 0.1 eV, respectively. From GeF4 the molecular ion GeF4- and the fragments GeF3-, GeF2-, GeF- and F- are all observed with appreciable intensities, and the F- production is found to be significantly close to 0 eV incident electron energy. The present findings are compared with earlier experiments and discussed in context to the thermochemistry of the respective processes as well as the nature of the underlying resonances. (C) 2013 Published by Elsevier B.V.