Filters

Results

**1**-**10**of**2915** Results

**1**-**10**of**2915**. Search took:**0.021**secondsSort by: date | relevance |

AbstractAbstract

[en] The L x-ray production cross sections for Gd and Tb obtained by proton impact in the energy range 250-400 keV have been measured. The theoretical calculations for these x-ray production cross sections have been performed by perturbed stationary state theory with relativistic, energy loss and Coulomb deflection corrections using the theoretical values for x-ray emission rates, subshell fluorescence yields and Coster-Kronig transition probabilities. Due to the lack of other experimental data, the present results have been compared with the theoretical predictions and are found to be in reasonable agreement. The intensity ratios are also presented. (author)

Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] Observations of resonant electron transfer and L-shell excitation (RTE) using coincidence techniques are reported for

_{41}Nb^{31+}and_{57}La^{40+}ions colliding with H_{2}. The measured RTE cross sections are about ten times larger than those previously found for RTE involving the K shell and constitute as much as half of the total Lαβ x-ray production. Overall agreement with theory is reasonable but discrepancies similar to those previously reported for K-shell RTE exist. The results demonstrate the importance of electron correlation in the production of L vacancies for projectile energies where RTE is possible. (author)Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] Elastic and inelastic cross sections, differential in energy loss and scattering angle, have been determined from the energy loss spectra of 1.5 - 25 keV He

^{+}scattered from atomic hydrogen at scattering angles from 5'-2^{0}(laboratory frame). The experimental results compare favourably with the experimental and theoretical data obtained at low incident energies by other authors, but for the higher energies, the present results exhibit a strong disagreement with many of the reported calculations. (author)Original Title

Mesure des sections efficaces differentielles elastique et inelastique pour la collision He

^{+}-H avec une energie de collision 1,5 <= E_{0}<= 25 keV et un angle de diffusion 5' <= thetasub(lab) <= 2^{0}Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] Experimental results for the integral alignment A

_{20}of H(2p) following collisions of hydrogen atoms with helium, neon and argon atoms are presented for projectile energies of 1-5 keV. In addition, we have measured as a function of impact parameter the differential (impact-parameter-dependent) alignment and orientation in 2 and 3 keV deuterium-helium collisions. The present results show fair agreement with recent theoretical calculations. (author)Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] The spectra of fluorescence depolarisation (orientation, alignment) applying to single collision conditions are analysed for the alkali-helium series. These are derived from a quantum calculation of the optical collision cross sections for non-resonant collision pair excitation. Strong spectral variations of the polarisation are found which reflect the potential characteristics of these systems. A numerical test is performed for the classical Lewis model using realistic trajectories and a reasonable choice of the decoupling radius, and fair quantitative agreement with the quantum calculation is shown. Large residual alignments in the far wings demonstrate a lack of complete reorientation of the transition dipole in a strong collision. In the red wing the effect of the coherent excitation of the two II components is apparent in the alignment for the smaller alkalis. The behaviour near the resonances is consistent with the prediction of the factorisation approximation, though for the extreme cases Li, Rb and Cs some of the limits are valid only in a very small range of detunings. (author)

Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] Photoionisation cross sections for excited nl states (n <20, l <= 4) of K and positive K-like ions have been computed in the framework of a non-relativistic single-electron model by the use of a central potential. The evolution of the non-hydrogenic behaviour of photoionisation cross sections near threshold is studied along a given nl series and along the K sequence. This evolution and the occurrence of minima and maxima in photoionisation cross sections are analysed in terms of the quantum defect theory. Radiative recombination coefficients for K-Ti

^{3+}, Fe^{7+}and Mo^{23+}have been obtained within the electron temperature range 500 <= T <= 10 000 K, by the use of the principle of detailed balance. The significant non-hydrogenic features are outlined and the systematics of the recombination of alkali atoms and alkali-like ions are analysed. Comparisons are made with the results of the hydrogenic model and with other available theoretical or experimental results. (author)Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Country of publication

CALCIUM IONS, CHROMIUM IONS, COMPARATIVE EVALUATIONS, CROSS SECTIONS, ELECTRON TEMPERATURE, ENERGY-LEVEL TRANSITIONS, EXCITED STATES, IRON IONS, KRYPTON IONS, MANGANESE IONS, MOLYBDENUM IONS, PHOTOIONIZATION, POTASSIUM, RECOMBINATION, SCANDIUM IONS, THEORETICAL DATA, TITANIUM IONS, VANADIUM IONS, ZINC IONS

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] Theoretical results on K-shell ionisation for a variety of asymmetric collision systems are reported. The calculated ionisation rates are compared with experimental data. The coupled-channel formalism underlying these calculations is presented. It is based on a set of relativistic target centred states, taking a screened potential of Dirac-Fock-Slater type into account. The effects of different matrix elements are discussed, e.g. continuum-continuum couplings. The binding effect is inherently contained in the present approach and described in a dynamical way. (author)

Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] Various forms of the half-on-shell Coulomb T matrix are used in the plane-wave impulse approximation to derive the differential cross section for the ionisation of an atomic target by electron impact. Comparison with absolute measurements on helium for small recoil momentum shows that the Ford half-shell T matrix, combined with a Hartree-Fock target wavefunction, gives much better agreement, over the energy range considered, than do the standard and regularized half-shell T matrices. (author)

Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] A ten-channel eikonal treatment of electron-helium collisions is performed for a basis set of (1

^{1}S, 2^{1}S, 2^{1}P, 3^{1}S, 3^{1}P and 3^{1}D) target states to yield the first theoretical results for the orientation and alignment parameters for the 3^{1}D level of helium. Good agreement with recent measurements is obtained. (author)Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] A general description of the data requirements for opacity calculations has been given in paper I. The present paper gives a detailed description of the methods being used in a collaborative effort which is referred to as the Opacity Project. The close-coupling approximation of electron-atom collision theory is used to calculate energies and wavefunctions for bound states, oscillator strengths, photoionisation cross sections and parameters for line broadening by electron impact. The computations are made using the R-matrix method together with new codes for calculating outer-region solutions and dipole integrals. Use of these techniques provides an efficient means of calculating large amounts of accurate atomic data. (author)

Primary Subject

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

1 | 2 | 3 | Next |