Positron–hydrogen ionizing collisions in the presence of a laser field

1982 ◽  
Vol 60 (4) ◽  
pp. 605-609 ◽  
Author(s):  
P. Cavaliere ◽  
C. Leone ◽  
G. Ferrante
Keyword(s):  
Angular Distribution ◽  
Electric Fields ◽  
Cross Sections ◽  
Laser Field ◽  
Single Mode ◽  
Forward Direction ◽  
Dipole Approximation ◽  
Theoretical Treatment ◽  
Wave Approximation ◽  
Hydrogen Ionization

Triple differential cross sections (TDC) for positron–hydrogen ionization in the presence of a laser field are derived within a treatment which uses the Coulomb–Born wave approximation. The laser field is treated classically in the dipole approximation and taken to be homogeneous and single mode. Calculations are specialized to the case of a coplanar asymmetric geometry. The presence of the laser is found to alter significantly the shape of the angular distribution of the ejected electrons when photon exchanges occur. Laser electric fields parallel to the positron transferred momentum [Formula: see text] increase the number of electrons ejected in the forward direction, compared to the no-field case. Laser electric fields perpendicular to Kif double the peaks present in the field-free angular distribution and rotate them symmetrically in opposite directions from the Kif axis towards the EL axis. The results for ionization by positrons are compared to those for ionization by electrons (within the same theoretical treatment). Differences are found only for [Formula: see text]. The limits of validity of the model are discussed, together with simple physical arguments to explain the modifications to the shape of the TDC.

Laser-induced Compton scattering from a bound electron

1992 ◽  
Vol 70 (1) ◽  
pp. 72-77 ◽  
Author(s):  
F. Ehlotzky
Keyword(s):  
Angular Distribution ◽  
Compton Scattering ◽  
Harmonic Generation ◽  
Cross Sections ◽  
Laser Field ◽  
Multiphoton Ionization ◽  
Ionization Threshold ◽  
Powerful Laser ◽  
Bound Electrons ◽  
Bound Electron

We investigate nonrelativistically Compton scattering by an electron bound in hydrogen in a powerful laser field. The corresponding nonlinear rates and cross sections are evaluated in a Keldysh-type of approximation and compared with the rates and cross sections of multiphoton ionization and harmonic generation. We find that multiphoton ionization overshadows Compton scattering by many orders of magnitude, however, Compton scattering may well compete with harmonic generation above the ionization threshold, since, in particular, both processes have the same angular distribution and only odd harmonics can be created by bound electrons, while in bound-free Compton scattering all harmonics will be generated.

Electron Scattering in Solids

1990 ◽  
Vol 48 (2) ◽  
pp. 4-5
Author(s):  
Ryuichi Shimizu ◽  
Ze-Jun Ding
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Angular Distribution ◽  
Elastic Scattering ◽  
Electron Scattering ◽  
Cross Sections ◽  
Expansion Method ◽  
Electron Excitation ◽  
Partial Wave Expansion ◽  
Backscattered Electrons

Monte Carlo simulation has been becoming most powerful tool to describe the electron scattering in solids, leading to more comprehensive understanding of the complicated mechanism of generation of various types of signals for microbeam analysis.The present paper proposes a practical model for the Monte Carlo simulation of scattering processes of a penetrating electron and the generation of the slow secondaries in solids. The model is based on the combined use of Gryzinski’s inner-shell electron excitation function and the dielectric function for taking into account the valence electron contribution in inelastic scattering processes, while the cross-sections derived by partial wave expansion method are used for describing elastic scattering processes. An improvement of the use of this elastic scattering cross-section can be seen in the success to describe the anisotropy of angular distribution of elastically backscattered electrons from Au in low energy region, shown in Fig.l. Fig.l(a) shows the elastic cross-sections of 600 eV electron for single Au-atom, clearly indicating that the angular distribution is no more smooth as expected from Rutherford scattering formula, but has the socalled lobes appearing at the large scattering angle.

scholarly journals LEvEL: Low-Energy Neutrino Experiment at the LHC

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Kevin J. Kelly ◽  
Pedro A. N. Machado ◽  
Alberto Marchionni ◽  
Yuber F. Perez-Gonzalez
Keyword(s):  
Cross Sections ◽  
Hadron Collider ◽  
Neutrino Flux ◽  
Coherent Scattering ◽  
Forward Direction ◽  
Low Energy ◽  
Neutrino Experiment ◽  
Beam Dump ◽  
Neutrino Production ◽  
Energy Neutrino

Abstract We propose the operation of LEvEL, the Low-Energy Neutrino Experiment at the LHC, a neutrino detector near the Large Hadron Collider Beam Dump. Such a detector is capable of exploring an intense, low-energy neutrino flux and can measure neutrino cross sections that have previously never been observed. These cross sections can inform other future neutrino experiments, such as those aiming to observe neutrinos from supernovae, allowing such measurements to accomplish their fundamental physics goals. We perform detailed simulations to determine neutrino production at the LHC beam dump, as well as neutron and muon backgrounds. Measurements at a few to ten percent precision of neutrino-argon charged current and neutrino-nucleus coherent scattering cross sections are attainable with 100 ton-year and 1 ton-year exposures at LEvEL, respectively, concurrent with the operation of the High Luminosity LHC. We also estimate signal and backgrounds for an experiment exploiting the forward direction of the LHC beam dump, which could measure neutrinos above 100 GeV.

scholarly journals Bistable dynamics beyond rotating wave approximation

2014 ◽  
Vol 23 (02) ◽  
pp. 1450019 ◽  
Author(s):  
Y. A. Sharaby ◽  
S. Lynch ◽  
A. Joshi ◽  
S. S. Hassan
Keyword(s):  
Ring Cavity ◽  
Dynamical Behavior ◽  
Single Mode ◽  
Unstable State ◽  
Nonlinear Dynamical ◽  
Rotating Wave Approximation ◽  
Wave Approximation ◽  
Atomic Medium ◽  
Bistable Dynamics ◽  
Rotating Wave

In this paper, we investigate the nonlinear dynamical behavior of dispersive optical bistability (OB) for a homogeneously broadened two-level atomic medium interacting with a single mode of the ring cavity without invoking the rotating wave approximation (RWA). The periodic oscillations (self-pulsing) and chaos of the unstable state of the OB curve is affected by the counter rotating terms through the appearance of spikes during its periods. Further, the bifurcation with atomic detuning, within and outside the RWA, shows that the OB system can be converted from a chaotic system to self-pulsing system and vice-versa.

Tunable localized surface plasmon resonances of asymmetric Au/SiO2/Au cross-shape nanobars

2014 ◽  
Vol 28 (17) ◽  
pp. 1450143 ◽  
Author(s):  
M. L. Wan ◽  
H. J. Du ◽  
Y. L. Song ◽  
F. Q. Zhou ◽  
K. J. Dai
Keyword(s):  
Electric Fields ◽  
Surface Plasmon ◽  
Near Infrared ◽  
Dipole Approximation ◽  
Localized Surface Plasmon ◽  
Surface Plasmon Resonances ◽  
Localized Surface Plasmon Resonances ◽  
Plasmon Resonances ◽  
Surface Enhanced Raman ◽  
Infrared Spectral

The plasmonic properties of asymmetric Au / SiO 2/ Au sandwiched cross-shape nanobars are investigated theoretically using the discrete dipole approximation (DDA) method. Two localized surface plasmon resonances are observed in the extinction spectra, which perform extreme sensitivity to the length and width of the nanobar and can be tuned easily throughout visible and into near-infrared spectral regions. The local electric fields around the nanobar are calculated and a pure electromagnetic Raman enhancement factor of about 106 can be achieved. In addition, compared to a monolayer gold nanobar, it exhibits more "hot spots" and stronger localized electric field enhancements. This plasmonic substrate provides potential applications in surface enhanced Raman scattering (SERS) and nonlinear optical devices.

Electron impact excitation of He 21P in the presence of a nonresonant laser field

1993 ◽  
Vol 71 (7-8) ◽  
pp. 326-333 ◽  
Author(s):  
B. Wallbank ◽  
J. K. Holmes ◽  
A. Weingartshofer
Keyword(s):  
Carbon Dioxide ◽  
Cross Sections ◽  
Differential Cross ◽  
Laser Field ◽  
Carbon Dioxide Laser ◽  
Impact Excitation ◽  
Incident Electron Energy ◽  
Electron Impact Excitation ◽  
Helium Atoms ◽  
Simultaneous Absorption

We report experimental differential cross sections for inelastic scattering of electrons from helium atoms in the presence of an intense (~108 W cm−2) carbon dioxide laser. The cross sections for excitation of the 21P state of helium with the simultaneous absorption or emission of one laser quantum were measured over the incident electron energy range of 36–70 eV and scattering angles of 13–31°.

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