scholarly journals Electron Momentum Spectroscopy

1986 ◽  
Vol 39 (5) ◽  
pp. 587 ◽  
Author(s):  
IE McCarthy
Keyword(s):  
Impulse Approximation ◽  
High Electron ◽  
Final States ◽  
Final State ◽  
Structure Information ◽  
Plane Wave Impulse Approximation ◽  
Ion Structure ◽  
Spectroscopic Factors ◽  
Electron Momentum Spectroscopy ◽  
Energy And Momentum

For sufficiently high electron energies (greater than a few hundred eV) and sufficiently low recoil momenta Oess than a few atomic units) the differential cross section for the non-coplanar symmetric (e,2e) reaction on an atom or molecule depends on the target and ion structure only through the target-ion overlap. Experimental criteria for the energy and momentum are that the apparent structure information does not change when the energy and momentum are varied. The plane-wave impulse approximation is a sufficient description of the reaction mechanism for determining spherically averaged squares of momentum-space orbitals for atoms and molecules and for coefficients describing initial- and final-state correlations. For mainly uncorrelated initial states, spectroscopic factors for final states belonging to the same manifold are uniquely determined. For molecules, summed spectroscopic factors can be compared for different ion manifolds. For atoms, summed spectroscopic factors and higher-momentum profiles require the dist~rted-wave impulse approximation.

Electron momentum spectroscopy experiments and calculations for the production of excited states of He+ and

1996 ◽  
Vol 74 (11-12) ◽  
pp. 748-756 ◽  
Author(s):  
N. Lermer ◽  
B. R. Todd ◽  
N. M. Cann ◽  
C. E. Brion ◽  
Y. Zheng ◽  
...  
Keyword(s):  
Excited States ◽  
Cross Section ◽  
Cross Sections ◽  
Impulse Approximation ◽  
Final State ◽  
Electron Momentum ◽  
Plane Wave Impulse Approximation ◽  
Highly Sensitive ◽  
Electron Momentum Spectroscopy ◽  
Explicitly Correlated

The (e,2e) cross-section for transitions to the n = 2 final state of He+ and the 2sσg, final state of [Formula: see text] have been measured, relative to the cross-section for the transitions to the respective ground state ions, using a highly sensitive momentum dispersive multichannel electron momentum spectrometer. The experimental results for He are compared with plane wave impulse approximation (PWIA) cross-section calculations carried out using two previously published GI wavefunctions and also with two cross-section calculations based on explicitly correlated wavefunctions with energy errors of less than 10 nHartree. The H2 results are compared with calculations by J.W. Liu and V.H. Smith Jr. (Phys. Rev. A, 31, 3003 (1985); erratum: Phys. Rev. A, 39, 3703 (1989)). For both He and H2, significant differences are observed between the measured relative cross-sections and those calculated using the PWIA. While the measurements for He differ from previous work, the results for H2 are consistent with some earlier measurements.

scholarly journals How to Explain the Difference between (?, e) and (e, 2e) Spectroscopic Factors

1991 ◽  
Vol 44 (3) ◽  
pp. 293 ◽  
Author(s):  
M Ya Amusia ◽  
AS Kheifets
Keyword(s):  
Atomic State ◽  
Final States ◽  
Electron Correlations ◽  
Atomic Shell ◽  
Initial State ◽  
Electron Momentum ◽  
Relative Line ◽  
Spectroscopic Factors ◽  
Electron Momentum Spectroscopy ◽  
The Difference

It is shown that the relative line intensity of the main and satellite lines in the atomic shell ionisation spectrum depends significantly on the mechanism responsible for the removal of the electron. This dependence is explained by the influence of many-electron correlations in the initial state of the atom to be ionised, which is considerable when the momentum transferred to the ion is large. This is the case for photoionisation, i.e. the (y, e) reaction under the condition of large photon energy. On the contrary, in electron momentum spectroscopy, such as the symmetric noncoplanar (e, 2e) reaction, the momentum transferred to the ion is typically small and the initial atomic state correlations are negligible. It follows from this that the spectroscopic factors of the different final states of the ion, as defined in the usual way, can be measured only for the (e,2e) reaction, whereas a more involved interpretation is necessary for the (y, e) reaction. Comparison of the calculated spectroscopic factors of Ar II and Xe II 2S ion eigenstates with recent (Y,e) and (e,2e) experimental data has confirmed this conclusion.

scholarly journals Application of DFT and EMS to the Study of Strained Organic Molecules

1998 ◽  
Vol 51 (4) ◽  
pp. 707 ◽  
Author(s):  
W. Adcock ◽  
M. J. Brunger ◽  
M. T. Michalewicz ◽  
D. A. Winkler
Keyword(s):  
Wave Function ◽  
Density Functional ◽  
Impulse Approximation ◽  
Basis Sets ◽  
Functional Theory ◽  
Electron Momentum ◽  
Plane Wave Impulse Approximation ◽  
Electron Momentum Spectroscopy ◽  
Momentum Distributions ◽  
Self Consistent Field

Electron momentum spectroscopy (EMS) studies of the valence shells of [1.1.1]propellane, 1,3-butadiene, ethylene oxide and cubane are reviewed. Binding energy spectra were measured in the energy regime of 3·5–46·5 eV over a range of different target electron momenta, so that momentum distributions (MDs) could be determined for each ion state. Each experimental electron momentum distribution is compared with those calculated in the plane wave impulse approximation (PWIA) using both a triple-? plus polarisation level self-consistent field (SCF) wave function and a further range of basis sets as calculated using density functional theory (DFT). A critical comparison between the experimental and theoretical momentum distributions allows us to determine the ‘optimum’ wave function for each molecule from the basis sets we studied. This ‘optimum’ wave function then allows us to investigate chemically or biologically significant molecular properties of these molecules. EMS-DFT also shows promise in elucidating the character of molecular orbitals and the hybridisation state of atoms.

scholarly journals Satellite Intensities in Photoelectron Spectroscopy and Electron Momentum Spectroscopy-Synchrotron Radiation Studies of Argon 3s and Xenon 5s Photoionisation (hv - 60?130 eV)

1986 ◽  
Vol 39 (5) ◽  
pp. 565 ◽  
Author(s):  
CE Brion ◽  
KH Tan
Keyword(s):  
Synchrotron Radiation ◽  
Photon Energy ◽  
Photoelectron Spectroscopy ◽  
Impulse Approximation ◽  
Main Line ◽  
Magic Angle ◽  
Electron Momentum ◽  
X Ray ◽  
Plane Wave Impulse Approximation ◽  
Electron Momentum Spectroscopy

Binding energy spectra for the main line, satellite lines and associated double ionization continuum for argon 3s and xenon 5s photoionisation have been measured in the photon energy range 60-130 eV using monochromatised synchrotron radiation and magic angle photoelectron spectroscopy. In particular the ratio of satellite to main line intensities has been investigated and compared with the results of earlier experiments using X-ray and ultraviolet photoelectron spectroscopy as well as with recent measurements by electron momentum [i.e. binary (e,2e)] spectroscopy. The results of the presently reported photoelectron measurements show that the satellite intensity relative to that of the main ns -1 line increases with increasing photon energy and approaches the value given by electron momentum spectroscopy. These findings are contrary to predictions based on recent calculations of photoelectron intensities. The present work lends support to the direct interpretation of satellite intensities (pole strengths or spectroscopic factors) in binary� (e, 2e) spectroscopy using the plane wave impulse approximation. The need for improved calculations of photoionisation intensities as well as further photoelectron measurements in the X-ray region is stressed.

scholarly journals Total cross section of the reaction γd → π–pp in the threshold energy region

2020 ◽  
Vol 64 (2) ◽  
pp. 159-163 ◽  
Author(s):  
E. S. Kokoulina ◽  
M. I. Levchuk ◽  
M. N. Nevmerzhitsky ◽  
R. G. Shulyakovsky
Keyword(s):  
Plane Wave ◽  
Total Cross Section ◽  
Cross Section ◽  
Cross Sections ◽  
Threshold Energy ◽  
Impulse Approximation ◽  
Final State ◽  
Plane Wave Impulse Approximation ◽  
Theoretical Predictions ◽  
Good Agreement

In the framework of the diagrammatic approach, the total cross section of near-threshold π– photoproduction on the deuteron is calculated. Contributions of the diagrams corresponding to the plane wave impulse approximation as well as to NN- and πN-interactions in the final state have been taken into account. We have compared the theoretical predictions with the results of the recent measurements performed at the MAX IV laboratory of the Lund University. There is good agreement with the data at photon energies from 147 to 155 MeV. However, at 158 and 160 MeV, the theoretical predictions significantly overestimate the measured cross sections.

scholarly journals A Procedure to Determine Dyson Orbitals from Electron Momentum Spectroscopy: Application to 1,2-Propadiene, 1,3-Butadiene, Cyclopropane and [1.1.1]Propellane

1998 ◽  
Vol 51 (4) ◽  
pp. 691 ◽  
Author(s):  
R. J. F. Nicholson ◽  
I. E. McCarthy ◽  
M. J. Brunger
Keyword(s):  
Inverse Method ◽  
Impulse Approximation ◽  
Reaction Model ◽  
Electron Momentum ◽  
Plane Wave Impulse Approximation ◽  
Molecular Systems ◽  
Hartree Fock ◽  
Fitting Procedure ◽  
Electron Momentum Spectroscopy ◽  
Measured Momentum

We employ a numerical inverse method of extracting the target-ion overlap, or normalised Dyson orbital, directly from experimental electron momentum spectroscopy data by using a quantum- mechanically constrained statistical fitting procedure. This method is used in conjunction with the previously verified, for molecular targets, plane wave impulse approximation (PWIA) reaction model. The present procedure was applied to previously measured momentum distributions (MDs) for the 2e′ and 1e′ valence orbitals of cyclopropane, the 7ag orbital of trans 1,3-butadiene, the 2e orbital of 1,2-propadiene and the 3a′1 orbital of [1.1.1]propellane. We note that this is the first extensive application of the present method to organic molecular systems. In each case the derived normalised Dyson orbital provided a superior representation of the experimental MD than did the corresponding Hartree-Fock orbital. The ramifications of this result are discussed in the text.

Charge exchange reactions on medium and heavy mass targets at intermediate energies

2019 ◽  
Vol 35 (08) ◽  
pp. 2050045
Author(s):  
Pardeep Singh ◽  
Monika Singh ◽  
Neha Rani
Keyword(s):  
Charge Exchange ◽  
Cross Sections ◽  
Energy Charge ◽  
Impulse Approximation ◽  
Mass Region ◽  
Intermediate Energy ◽  
Exchange Reactions ◽  
Plane Wave Impulse Approximation ◽  
Text Type ◽  
Intermediate Energies

The nuclear isotopic structure can be understood easily via the intermediate-energy charge exchange reactions of (p, n) and [Formula: see text]He, [Formula: see text] type. In the current contribution, we present some results for charge exchange reactions induced by 3He on targets lying in mass region [Formula: see text] within the theoretical framework of plane wave impulse approximation (PWIA) and distorted wave impulse approximation (DWIA). Here, the recoil effects in PWIA have also been considered. Particularly, the angular distributions and the unit cross-sections have been calculated and compared with the available data. Further, the importance of inclusion of the exchange contribution in these reactions is also considered, which eventually enhance the matching with data.

scholarly journals RECENT τ LEPTON RESULTS FROM BABAR

2014 ◽  
Vol 35 ◽  
pp. 1460440
Author(s):  
ALBERTO LUSIANI
Keyword(s):  
Standard Model ◽  
Branching Fractions ◽  
Charged Particles ◽  
Babar Collaboration ◽  
Final States ◽  
Final State ◽  
Experimental Knowledge ◽  
Electron Positron ◽  
The Standard Model ◽  
Positron Collisions

We report recent measurements on τ leptons obtained by the BABAR collaboration using the entire recorded sample of electron-positron collisions at and around the Υ(4S) (about 470fb-1). The events were recorded at the PEP-II asymmetric collider at the SLAC National Accelerator Laboratory. The measurements include high multiplicity τ decay branching fractions with 3 or 5 charged particles in the final state, a search for the second class current the τ decay τ → πη′ν, τ branching fractions into final states containing two KS mesons, [Formula: see text], with h = π, K, and preliminary measurements of hadronic spectra of τ decays with three hadrons (τ- → h-h+h-ντ decays, where h = π, K). The results improve the experimental knowledge of the τ lepton properties and can be used to improve the precision tests of the Standard Model.

SEARCH FOR NEW PHYSICS IN eμX DATA AT THE TEVATRON USING SLEUTH: A QUASI-MODEL-INDEPENDENT SEARCH STRATEGY FOR NEW PHYSICS

2001 ◽  
Vol 16 (supp01b) ◽  
pp. 888-890
Author(s):  
◽  
BRUCE KNUTESON
Keyword(s):  
Standard Model ◽  
Search Strategy ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Final States ◽  
Final State ◽  
The Standard Model ◽  
Model Independent

We present a quasi-model-independent search for physics beyond the standard model. We define final states to be studied, and construct a rule that identifies a set of variables appropriate for any particular final state. A new algorithm ("Sleuth") searches for regions of excess in the space of those variables and quantifies the significance of any detected excess. After demonstrating the sensititvity of the method, we apply it to the semi-inclusive channel eμX collected in ≈108 pb -1 of [Formula: see text] collisions at [Formula: see text] at the DØ experiment at the Fermilab Tevatron. We find no evidence of new high pT physics in this sample.

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