Absolute elastic differential cross sections for electron scattering by C6H5CH3 and C6H5CF3 at 1.5–200 eV: a comparative experimental and theoretical study with C6H6

We present absolute differential cross sections DCS for elastic scattering from two benzene derivatives C6H5CH3 and C6H5CF3. The crossed-beam method was used in conjunction with the relative flow technique using helium as the reference gas to obtain absolute values. Measurements were carried out for scattering angles 15° –130° and impact energies 1.5–200 eV. DCS results for these two molecules were compared to those of C6H6 from our previous study. We found that 1 these three molecules have DCS with very similar magnitudes and shapes over the energy range 1.5–200 eV, although DCS for C6H5CF3 increase steeply toward lower scattering angles due to the dipole moment induced long-range interaction at 1.5 and 4.5 eV, and 2 that the molecular structure of the benzene ring significantly determines the collision dynamics. From the measured DCS, elastic integral cross sections have been calculated. Furthermore, by employing a corrected form of the independent-atom method known as the screen corrected additive rule, DCS calculations have been carried out without any empirical parameter fittings, i.e., in an ab initio nature. Results show that the calculated DCS are in excellent agreement with the experimental values at 50, 100, and 200 eV

Electron-collision cross sections for iodine

We present results from a joint experimental and theoretical study of elastic electron scattering from atomic iodine. The experimental results were obtained by subtracting known cross sections from the measured data obtained with a pyrolyzed mixed beam containing a variety of atomic and molecular species. The calculations were performed using both a fully relativistic Dirac B-spline R-matrix (close-coupling) method and an optical model potential approach. Given the difficulty of the problem, the agreement between the two sets of theoretical predictions and the experimental data for the angle-differential and the angle-integrated elastic cross sections at 40 eV and 50 eV is satisfactory

DO-D Bond Dissociation Energy

This work was also supported by the Radiation Biology and Biophysics Doctoral Training Programme (RaBBiT, PD/00193/2012). P.L.-V. also acknowledges his visiting professor position at Sophia University. The computations were enabled by resources provided by the Swedish National Infrastructure for Computing (SNIC) at Chalmers Centre for Computational Science and Engineering (C3SE) and partially funded by the Swedish Research Council through Grant Agreement 2020-05293. G.G. acknowledges partial financial support from the Spanish Ministerio de Ciencia e Innovación (Project PID2019-104727RB-C21), Ministerio de Universidades (Project PRX21/00340), and CSIC (Project LINKA20085). The work is part of COST Action CA18212 - Molecular Dynamics in the GAS phase (MD-GAS). Publisher Copyright: © 2023 The Authors. Published by American Chemical Society.H2O/D2O negative ion time-of-flight mass spectra from electron transfer processes at different collision energies with neutral potassium yield OH-/OD-, O-, and H-/D-. The branching ratios show a relevant energy dependence with an important isotope effect in D2O. Electronic state spectroscopy of water has been further investigated by recording potassium cation energy loss spectra in the forward scattering direction at an impact energy of 205 eV (lab frame), with quantum chemical calculations for the lowest-lying unoccupied molecular orbitals in the presence of a potassium atom supporting most of the experimental findings. The DO-D bond dissociation energy has been determined for the first time to be 5.41 ± 0.10 eV. The collision dynamics revealed the character of the singly excited (1b2-1) molecular orbital and doubly excited states in such K-H2O and K-D2O collisions.publishersversionpublishe

Correction to “Isotope Effect in D2O Negative Ion Formation in Electron Transfer Experiments: DO–D Bond Dissociation Energy”

In a recent Letter,1 a set of minor inconsistencies have been found in the main body text and in the Supporting Information files; these are now thoroughly corrected. Thus, we highlight the sections where these changes apply. ¦ MAIN MANUSCRIPT BODY TEXT Abstract: The DO-D bond dissociation energy has been reported to be 5.41 ± 0.10 eV, while considering EA(O) in the original manuscript. However, EA(OD) should be used instead, thus leading to a bond dissociation energy of 5.28 ± 0.20 eV. Page 5365, left column, second paragraph; “From the appearance...” is reorganized and reads as follows: Taking the values in Table S4 together with the BDE, the enthalpy of reaction can be obtained from ?Hr(OH-) = D(H-OH) - EA(OH) = 3.34 eV. In the charge transfer process, if we add the potassium ionization energy, OH- is expected at 7.68 eV. The reactions threshold was obtained assuming no excess energy (E#), yet momentum conservation of the dissociating partners may impact on the lighter fragment kinetic energy, thus shifting the energy to a higher value. We note a difference of ~1.1 eV for the energy loss data, which is certainly plausible given the kinetic-energy release distribution of H- in Figure S3. Thus, from the appearance energy (AE) in the H2O energy loss spectrum (Figure 2) at ?E ˜ 8.8 eV, one can obtain the HO-H bond dissociation energy (BDE) by taking the potassium ionization energy and the data from Table S4,2 i.e., D(HO-H) = AE(OH-) - IE(K) + EA(OH) - E#, yielding therefore D(HO-H) = 5.19 ± 0.20 eV which is in good agreement with the values 5.15 eV (118.81 ± 0.07 kcal/ mol)3 and 5.17 eV.4 Following the same approach for D2O, the energy loss spectrum shows a threshold feature at ?E ˜ 9.0 eV. We obtain for the first time the DO-D bond dissociation energy to be D(DO-D) = 5.28 ± 0.20 eV. In D2O the DO-D energy value is slightly higher than the O-D bond dissociation energy (5.176 eV5), which is in agreement with its analogue H2O. Page 5366, right column, last paragraph; “Electronic state spectroscopy...” reads as follows: The electronic state spectroscopy of H2O/D2O was thoroughly discussed from the experimental K+ energy loss spectra obtained, from which the DO-D bond dissociation energy has been obtained for the first time to be 5.28 ± 0.20 eV. ¦ SUPPORTING INFORMATION Enthalpies of formation (?fHg°) in reactions 2a.1-2b.2 and 4a.1-4b.2 are actually enthalpies of reaction (?Hr). Table S2 decimal places for O- and OH- from H2O have been corrected; they now read 12.08 ± 0.20 and 7.80 ± 0.20

Isotope Effect in D2O Negative Ion Formation in Electron Transfer Experiments: DO-D Bond Dissociation Energy.

H2O/D2O negative ion time-of-flight mass spectra from electron transfer processes at different collision energies with neutral potassium yield OH-/OD-, O-, and H-/D-. The branching ratios show a relevant energy dependence with an important isotope effect in D2O. Electronic state spectroscopy of water has been further investigated by recording potassium cation energy loss spectra in the forward scattering direction at an impact energy of 205 eV (lab frame), with quantum chemical calculations for the lowest-lying unoccupied molecular orbitals in the presence of a potassium atom supporting most of the experimental findings. The DO-D bond dissociation energy has been determined for the first time to be 5.41 ± 0.10 eV. The collision dynamics revealed the character of the singly excited (1b2-1) molecular orbital and doubly excited states in such K-H2O and K-D2O collisions

Electron and positron scattering cross sections for propene and cyclopropane

In this paper we investigate electron and positron total and electron vibrational excitation scattering cross sections for propene and cyclopropane molecules. The electron and positron total cross sections were measured over the energy range 0.2-1000 eV using a retarding-potential time-of-flight method while the electron impact vibrational excitation cross sections were measured using a crossed-beam method. For both molecules, bending and stretching vibrational modes are studied at loss energies 0.12 and 0.37 eV, respectively, for propene, and 0.13 and 0.37 eV, respectively, for cyclopropane, at the scattering angle of 90° and impact energy range 1-16 eV

Magnetic field-free measurements of the total cross sections for positron-neon and positron-argon scattering

Magnetic field-free measurements of the total cross sections for positron-neon and positron-argon scattering have been performed using an electrostatic high-brightness slow positron beam apparatus