Inelastic Electron Scattering Cross Sections Research Articles

Nickel carbonyl adsorption on the Ni(111) surface

Overlayers formed by the adsorption of Ni(CO) 4 in CO on the Ni(111) surface at 100 K were characterized using high resolution electron energy loss spectroscopy and thermal desorption spectroscopy. At temperatures below 135 K, molecular nickel carbonyl adsorbs on the CO saturated Ni(111) surface as suggested by several observations. Vibrational transitions characteristic of molecular Ni(CO) 4 are dominant. The energy dependence of both the elastic and inelastic electron scattering cross sections are dramatically altered by Ni(CO) 4 adsorption. All of the mass spectrometer ionization fragments typical of molecular Ni(CO) 4 are observed in the narrow thermal desorption peak at 150 K. The inelastic scattering cross sections for both adsorbed nickel carbonyl and adsorbed CO on the Ni(111) surface suggest that a nonresonant dipole scattering mechanism is dominant.

Nickel carbonyl adsorption on the Ni(111) surface

Overlayers formed by the adsorption of Ni(CO) 4 in CO on the Ni(111) surface at 100 K were characterized using high resolution electron energy loss spectroscopy and thermal desorption spectroscopy. At temperatures below 135 K, molecular nickel carbonyl adsorbs on the CO saturated Ni(111) surface as suggested by several observations. Vibrational transitions characteristic of molecular Ni(CO) 4 are dominant. The energy dependence of both the elastic and inelastic electron scattering cross sections are dramatically altered by Ni(CO) 4 adsorption. All of the mass spectrometer ionization fragments typical of molecular Ni(CO) 4 are observed in the narrow thermal desorption peak at 150 K. The inelastic scattering cross sections for both adsorbed nickel carbonyl and adsorbed CO on the Ni(111) surface suggest that a nonresonant dipole scattering mechanism is dominant.

The effects of triaxial deformations in the structure of the 2 (1)+ transition charge density in 58Ni

Inelastic electron scattering cross sections have been measured up to a momentum transfer q=3.9 fm −1, determining very precisely the transition charge density of the first excited 2 (1) + state of 58Ni. The results have been interpreted in a fully self-consistent theoretical treatment for both the ground state and the 2 (1) + transition charge density of 58Ni. The model applied is a collective description where the dynamics of the motion induces a non-zero deformation with nearly maximum triaxiality ( γ=30°). It is found that an adjustment of the collective wave function is needed to reproduce the measured transition charge density.

Elastic and inelastic electron scattering fromCr50,52,54

Elastic and inelastic electron scattering cross sections are given for $^{50,52,54}\mathrm{Cr}$ at momentum transfers between 0.15 and 2.6 ${\mathrm{fm}}^{\ensuremath{-}1}$. Ground state charge distributions are derived from a combined analysis of these data and muonic atom data. Deduced values of the rms charge radii are given. Comparison is made between the experimental charge distributions and density dependent Hartree-Fock-Bogolyubov calculations. Inelastic scattering form factors for ${2}^{+}$, ${4}^{+}$, and ${6}^{+}$ states up to 4 MeV excitation are given along with shell model and phenomenological model fits to those data, $B(\mathrm{EL})$ values, multipole dependence of effective charges, and other model parameters.NUCLEAR REACTIONS $^{50,52,54}\mathrm{Cr}(e, {e}^{\ensuremath{'}})$, $E=30\ensuremath{-}400$ MeV. Measured $\ensuremath{\sigma}(E, \ensuremath{\theta})$. Deduced ground state charge distributions compared to Hartree-Fock. Deduced inelastic form factors compared to shell model.

Polarisation propagator study of the electron impact excitation of the beryllium isoelectronic sequence

The second-order polarisation propagator approximation has been used to calculate the generalised oscillator strength f(K) for the 1S to 1P transitions of B II, C III, N iV and O V. The inelastic electron scattering cross section has been deduced for incident energies from 50 to 1000 eV. The results are compared with experimental ones and other calculations.

Polarization propagator study of the electron impact 2s2(1s)→ 2s2p(1p) transition of the beryllium atom

The second-order polarisation propagator approximation has been used to calculate the generalized oscillator strength f(K) for the 1S→ 1P transition of Be for K2 from 0 to 4 au. The inelastic electron scattering cross section has also been calculated for incident energies from 50 to 1000 eV. Agreement with published calculations and experimental results is good.

High-spin states ofJπ=12−, 14−inPb208studied by (e,e′)

Inelastic electron scattering cross sections for the excited states at 6.43, 6.74, and 7.06 MeV in /sup 208/Pb were measured with high resolution. The measurements were done in forward and backward directions covering the momentum transfer range of 0.3 < q < 2.5 fm/sup -1/. The state at 7.06 MeV was identified as the ..pi.. (i/sub 13/2/h/sub 11/2//sup-1/)/sub 12/- and the states at 6.74 and 6.43 MeV as the ..nu.. (j/sub 15/2/i/sub 13/2//sup -1/)/sub 14/-/sub ,12/- respectively. The identification was based on four criteria: (a) the agreement between the q dependence of the measured form factor with that of Hartree-Fock single particle-hole prediction, with no adjustment of radial parameters, (b) the absence of a longitudinal form factor, (c) the relative magnitude of the observed levels, and (d) the excitation energies being close to the single p-h energies. The measured strength of each state was found to be 50% of the single p-h prediction.

A critical evaluation of high energy electron impact spectroscopy to measure Compton profiles

The authors present high precision Compton profile measurements on helium and molecular hydrogen obtained by high energy electron impact spectroscopy. Inelastic electron scattering cross sections at 35 keV incident energy have been studied for both He and H2 over the momentum transfer range of 1.5-12.5 au. It is shown that there is a disparity between the energy-loss spectra converted to Compton profiles by means of the binary encounter theory and the theoretical Compton profile. This discrepancy displays itself as an asymmetry of the profile and a shift of the peak to a lower energy loss, known as the 'Compton defect'. A critical evaluation of the technique, improvements made over the previous electron Compton work, the method of data analysis and a rigorous test of the binary encounter theory will be discussed in detail. The authors also analyse the problem of multiple scattering.

Electron Scattering onPb207and the Induced Charge of the Neutron

High-resolution inelastic electron-scattering cross sections from /sup 207/Pb have been measured in the range of momentum transfer 0.37 fm/sup -1/ < or = q < or = 2.30 fm/sup -1/. Form factors have been extracted for low-lying neutron hole states and some-particle, two-hole states. Models for the induced charge of the neutron are compared with the data.

Dipole spectrum, sums and properties of ground-state methane and their relation to the molar refractivity and dispersion energy constant

Experimental and theoretical photo-absorption and high energy inelastic electron scattering cross sections, together with refractivity and sum rule constraints, are used to construct the non-relati...

Transition charge densities of low-lying collective states in even Zn isotopes

The inelastic electron scattering cross sections for the quadrupole transitions to the 2 1 + and 2 2 + states in the even Zn isotopes 64Zn, 66Zn and 68Zn and for the hexadecapole transition to the 4 + 1 state in 64Zn have been measured in a momentum transfer range up to q = 2.2 fm −1. In the frame-work of the vibrational model these states are considered as one- and two-quadrupole-phonon states. The measurements are characterized by high statistical accuracy and by an overall resolution of δE/ E 0 = 10 −3 which permitted separation of almost all members of the two-phonon triplet. The measured cross sections are analyzed with phenomenological models as well as with a Fourier-Bessel expansion of the transition charge density. The latter analysis yields realistic error bands for the transition charge densities and model-independent values for the reduced transition probabilities and transition radii.

Inelastic electron scattering from hydrogen at 50° and 60°

Inelastic electron scattering cross sections have been measured for four-momentum transfers between 4.1 GeV 2 and 30.5 GeV 2. At the large scattering angles of this experiment, the dominant contribution to the cross section comes from the W 1 structure function. In the conventional scaling variables, x and x′, this structure function does not exhibit scaling behavior, and at fixed x or x′ it is found to decrease with increasing four-momentum transfer.

Electron scattering studies of low-lying collective states of even Zn isotopes

The inelastic electron scattering cross sections for the excitation of the low-lying collective states in the even Zn isotopes 64Zn, 66Zn, 68Zn and 70Zn have been measured in the momentum transfer region q = 0.3–1.1 fm −1. Strong transitions to the first 2 + and 3 − states have been observed and the modified Tassie model with a two parameter Fermi charge distribution for the ground state was used to extract the values for the reduced transition probability B↑ (E λ). Besides the investigation of these states, which in the framework of the vibrational model are considered as one-phonon states, special effort was made to measure the transition to the 2 + two-phonon states in 64Zn ( ε = 1.80 MeV) and 70Zn ( ε = 1.76 MeV). We have applied the anharmonic vibrator model to these two nuclei and have extracted values for the static quadrupole moment of the first excited state.

The determination of the nuclear ground state and transition charge density from measured electron scattering data

The evaluation of elastic and inelastic electron scattering cross sections is discussed in terms of the Fourier-Bessel expansion of the nuclear ground state and transition charge density, respectively. The method allows one to deduce the charge distributions and the moments as well as the corresponding errors, which originate on the one hand from the uncertainties in the measured data and on the other hand from the lack of knowledge about the large- q behaviour of the form factors; these two contributions are determined separately. The method is described and proved with an evaluation of pseudodata and then applied to 208Pb cross sections. For this nucleus, detailed results concerning the possible structure of the charge density are presented.

Electron Beam Excitation and Damage of Biological Molecules; Its Implications for Specimen Damage in Electron Microscopy

Radiation damage of various biological molecules is measured in an ultra-high vacuum scanning microscope. The damage measurements are made using radiation-induced changes in electron energy-loss spectra and in electron diffraction patterns. Damage cross sections are compared with previously measured, inelastic electron-scattering cross sections. Using the measured damage doses, comparisons are made with the doses necessary for electron microscopy of biological specimens.

Measurements of Inelastic Electron Scattering Cross Sections near the One-Pion Threshold

The cross sections for single-arm inelastic electron-proton scattering were measured near the one-pion threshold for six values of ${q}^{2}$ between 0.23 and 1.84 Ge${\mathrm{V}}^{2}$. We determined the cross sections for nonresonant pion production and, using a particular formulation of soft-pion theory, extracted the normalized axial-vector form factor of the nucleon, $\frac{{G}_{A}({q}^{2})}{{G}_{A}(0)}$.

The correction of coincidence electron-scattering cross sections for radiative effects

The correction of inelastic electron-scattering cross sections for the effects of radiation is considered for experiments in which one of the final-state hadrons is detected in coincidence with the scattered electron. The results are expressed in terms of the missing mass of the unobserved particles. The accuracy of some commonly used approximations is investigated in the case of the ep → ep π 0 reaction in the region of the Δ (1236) resonance.

Measurements of large angle inelastic scattering cross sections for electrons on helium

The ratios of the inelastic electron scattering cross sections for the n=2 levels of helium to the corresponding elastic scattering cross sections have been measured in a crossed beam apparatus over the 30 degrees to 150 degrees range for incident energies of 82 and 200 eV. In both cases, at angles greater than 40 degrees the ratio of the sum of the inelastic cross sections to the elastic cross section was constant at a few percent in qualitative agreement with a similar experiment in atomic hydrogen by Williams. The four n=2 states were observed to have markedly different angular dependencies at 82eV incident energies. Only the 1S and 1P states were important at 200eV; the ratio 1S/1P was very nearly 2 at all angles larger than 60 degrees . Within experimental error, over the range of variables studied, the observed cross sections agreed with those predicted by the first born approximation only for 1P at angles less than 45 degrees at 82eV incident energy and for 1S and 1P at 30 degrees and 200eV incident energy.

Inelastic Electron Scattering from 18O

The inelastic electron scattering cross sections for the excitation of the levels in 18O lying below 6.0 MeV have been measured in the momentum transfer range 0.5 &lt; q &lt; 1.0 fm−1. Excitation of the following T = 1 levels was observed: 1.98 MeV (2+), 3.63 MeV (0+), 3.92 MeV (2+), 4.45 MeV (1−), 5.09 MeV (3−), 5.25 MeV (2+), and 5.33 MeV (0+). Estimates of transition probabilities to the ground state have been made through a parameterization of the data using the generalized Helm model. Longitudinal form factors calculated from the wave functions of Benson and Irvine show excellent agreement with the experimental form factors.

Electroproduction of single pions near threshold

Inelastic electron scattering cross sections from hydrogen have been measured near the pion production threshold at electron four-momentum transfers squared of 0.10, 0.14. 0.19 and 0.31 (GeV/ c) 2 using a beam of 2 GeV/ c electrons from the Daresbury electron synchrotron and a magnetic spectrometer to detect the scattered electron. The results are analysed phenomenologically, and compared with theoretical calculations, using current algebra, to provide an estimate of the axial-vector form factor.