scholarly journals Excitation of Atomic Hydrogen by Proton Impact in the Presence of a Resonant Laser Field Using the First Order Magnus Approximation

1992 ◽  
Vol 45 (1) ◽  
pp. 47 ◽  
Author(s):  
Bhupat Sharma ◽  
Man Mohan
Keyword(s):  
Laser Beam ◽  
Computer Time ◽  
Dipole Approximation ◽  
Collision Dynamics ◽  
Hydrogen Atoms ◽  
Close Coupling ◽  
First Order ◽  
Resonant Laser ◽  
Atom Interaction ◽  
Transverse Polarisation

We consider proton collisions from hydrogen atoms in the presence of a laser beam (taken in the electric dipole approximation) that resonantly (or nearly resonantly) excites the hydrogen atoms from the Is to the 2p state. The laser beam is linearly polarised with polarisation either parallel (longitudinal) or perpendicular (transverse) to the direction of incidence of the proton. A non-perturbative quasi-energy approach is used to describe the laser-atom interaction, while the first-order Magnus approximation is used to describe the collision dynamics in the presence of the nearly resonant laser beam. We have calculated the integrated cross section o-(2s} for the excitation of the 2s state. It is found that 0-(2s} is small for longitudinal polarisation, as compared with transverse polarisation. We have also compared our field-free results obtained by using the first-order Magnus approximation to that obtained by the close-coupling approximation. Although both methods give excellent results, the former method is quite demanding in terms of computer time.

Laser beam scattering by bacterial cells: application of the discrete dipole approximation

2000 ◽  
Author(s):  
Aleksei E. Balaev ◽  
Valeri A. Doubrovski ◽  
K. N. Dvoretski
Keyword(s):  
Laser Beam ◽  
Dipole Approximation ◽  
Discrete Dipole Approximation ◽  
Bacterial Cells ◽  
Beam Scattering

Influence of Multidirectional Irregular Wave Sampling to Second-Order Hydroelastic Responses of VLFS

2009 ◽  
Author(s):  
Xujun Chen ◽  
Torgeir Moan ◽  
Xuefeng Tang
Keyword(s):  
Computer Time ◽  
Second Order ◽  
Irregular Waves ◽  
Floating Structure ◽  
First Order ◽  
Fluid Forces ◽  
Irregular Wave ◽  
Very Large Floating Structure ◽  
Principal Coordinates ◽  
Hydroelastic Response

Hydroelasticity theory considering the second-order fluid forces induced by the coupling of first-order wave potentials is introduced briefly in this paper. Based on this theory, four types of multidirectional irregular wave samplings are introduced, the frequency steps Δω of the four samplings are 0.04, 0.04, 0.02 and 0.01 rad/s, and the corresponding numbers of wave components N are 17, 75, 147 and 285 respectively. The result of principal coordinates and displacements of a very large floating structure (VLFS) for the four types of sampling are presented and discussed. The influence of the sampling is analyzed. The conclusions show that the sampling of the multidirectional irregular waves influence the second-order hydroelastic response of the VLFS. The accuracy and the computer time of the calculating with sampling of frequency step Δω = 0.02 rad/s are acceptable.

Derivation of the dipole approximation from the exact transition probabilities for hydrogen atoms

1975 ◽  
Vol 11 (6) ◽  
pp. 2196-2197
Author(s):  
H. E. Moses
Keyword(s):  
Transition Probabilities ◽  
Dipole Approximation ◽  
Hydrogen Atoms

First-order layout of a two-lens varifocal objective focusing a CO2 laser beam in a post-objective three-axis scanner

Optik ◽  
2011 ◽  
Vol 122 (10) ◽  
pp. 914-918 ◽  
Author(s):  
Vincenzo Greco ◽  
Luciana Bertoncini
Keyword(s):  
Laser Beam ◽  
Co2 Laser ◽  
First Order

scholarly journals Excitation and charge transfer in low-energy hydrogen atom collisions with neutral carbon and nitrogen

2019 ◽  
Vol 625 ◽  
pp. A78 ◽  
Author(s):  
A. M. Amarsi ◽  
P. S. Barklem
Keyword(s):  
Charge Transfer ◽  
Neutral Hydrogen ◽  
Stellar Atmospheres ◽  
Low Energy ◽  
Rate Coefficients ◽  
Collision Dynamics ◽  
Hydrogen Atoms ◽  
Stellar Spectra ◽  
Zero Rate ◽  
Excitation Processes

Low-energy inelastic collisions with neutral hydrogen atoms are important processes in stellar atmospheres, and a persistent source of uncertainty in non-LTE modelling of stellar spectra. We have calculated and studied excitation and charge transfer of C I and of N I due to such collisions. We used a previously presented method that is based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions for the adiabatic potential energies, combined with the multichannel Landau-Zener model for the collision dynamics. We find that charge transfer processes typically lead to much larger rate coefficients than excitation processes do, consistent with studies of other atomic species. Two-electron processes were considered and lead to non-zero rate coefficients that can potentially impact statistical equilibrium calculations. However, they were included in the model in an approximate way, via an estimate for the two-electron coupling that was presented earlier in the literature: the validity of these data should be checked in a future work.

HIGH FREQUENCY LIMITS OF THE TWO-ELECTRON PHOTOIONIZATION CROSS SECTIONS

2002 ◽  
Vol 09 (02) ◽  
pp. 1161-1166 ◽  
Author(s):  
R. KRIVEC ◽  
M. YA. AMUSIA ◽  
V. B. MANDELZWEIG
Keyword(s):  
Wave Function ◽  
Excited States ◽  
Cross Sections ◽  
High Frequency ◽  
Nuclear Charge ◽  
Principal Quantum Number ◽  
Dipole Approximation ◽  
Wave Functions ◽  
Initial State ◽  
First Order

Several cross sections of two-electron processes at high but nonrelativistic photon energies ω are considered, which are expressed solely via the initial state wave function of the ionized two-electron object. The new high precision and locally correct nonvariational wave functions describing the ground and several lowest excited states of H -, He and helium-like ions are used in calculations of different cross sections in the pure dipole approximation and with account of first order corrections in ω/c2, and a number of the cross sections' ratios. The dependencies of all these quantities on the nuclear charge Z and the principal quantum number n (for 1 < n < 5) of the initial state excitation are studied.

Angular and polarization effects in relativistic potential scattering of electrons in a powerful laser field

1999 ◽  
Vol 77 (8) ◽  
pp. 591-602 ◽  
Author(s):  
P Panek ◽  
J Z Kamiñski ◽  
F Ehlotzky
Keyword(s):  
Laser Field ◽  
Potential Scattering ◽  
Dipole Approximation ◽  
Powerful Laser ◽  
Scattered Electron ◽  
Electromagnetic Plane Wave ◽  
Polarization Effects ◽  
Nonrelativistic Case ◽  
First Order ◽  
Spin Effects

In view of recent advances in the development of powerful laser sources renewed interest has been devoted to the investigation of electron-scattering processes in very strong laser fields. Here, were consider the scattering of electrons by a potential in a strong electromagnetic plane wave. Since to a first order of approximation spin effects can be neglected, we describe the scattered electron by a laser-dressed Klein-Gordon particle. It is shown in a first-order Born approximation that at nearly relativistic scattering conditions, in which the space-dependence of the laser field cannot be ignored, characteristic angular and polarization effects can be encountered for specific scattering configurations that will not show up in the nonrelativistic case where the radiation field is treated in the dipole approximation. We also demonstrate that even for laser-field intensities at which nonrelativistic calculations should apply one can observe discrepancies between relativistic and nonrelativistic results.PACS Nos.: 34.50.Rk, 34.80.Qb, 32.80.Wr

Analyzing the quality of the first order diffracted laser beam emerging from an acousto-optic modulator

1985 ◽  
Vol 17 (2) ◽  
pp. 102-103 ◽  
Author(s):  
D. Pantzer ◽  
J. Politch ◽  
L. Ek
Keyword(s):  
Laser Beam ◽  
Acousto Optic Modulator ◽  
First Order

First-order exchange approximation

1963 ◽  
Vol 276 (1366) ◽  
pp. 346-353 ◽  
Keyword(s):  
Elastic Scattering ◽  
Cross Sections ◽  
Born Approximation ◽  
Scattering Amplitude ◽  
Wave Functions ◽  
Hydrogen Atoms ◽  
Final State ◽  
First Order ◽  
Exchange Approximation ◽  
Exchange Scattering

It is shown that when the Born approximation is applied to rearrangement collisions in the customary way, terms of the first order in the interaction energy between the colliding particles are omitted from the exchange scattering amplitude. If these terms are retained the arbitrariness which arises from the lack of orthogonality between the initial and final state wave functions is removed. The first-order exchange approximation derived in the present paper is employed to calculate the cross-sections for the 1 s -2 s and 1 s -2 p excitations of hydrogen atoms by electron impact and the elastic scattering of electrons by hydrogen atoms.

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