Generalized oscillator strength for Na 3s-3p transition

Generalized oscillator strengths (GOS's) for the Na $3s -3p$ transition have been investigated using the spin-polarized technique of the random phase approximation with exchange (RPAE) and the first Born approximation (FBA), focussing our attention on the position of the minimum. Intershell correlations are found to influence the position of the minimum significantly, but hardly that of the maximum. The RPAE calculation predicts for the first time the positions of the minimum and maximum at momentum transfer, $K$ values of 1.258 a.u. and 1.61 a.u., respectively. The former value is within the range of values extracted from experimental measurements, $K=1.0-1.67$ a.u.. We recommend careful experimental search for the minimum around the predicted value for confirmation.Comment: 11 pages, 2figure

Correlation structure in nondipole photoionization

The nondipole parameters that characterize the angular disribution of the photoelectrons from the 3d subshell of Cs are found to be altered qualitatively by the inclusion of correlation in the form of interchannel coupling between the $3d_{3/2}$ and $3d_{5/2}$ photoionization channels. A prominent characteristic maximum is predicted only in the parameters for $3d_{5/2}$ photoionization, while the effect for $3d_{3/2}$ is rather weak. The results are obtained within the framework of the Generalized Random Phase Approximation with Exchange (GRPAE), which in addition to the RPAE effects takes into account the rearrangement of all atomic electrons due to the creation of a 3d vacancy

Minima in generalized oscillator strengths of atomic transitions and the approach to the high-energy limit

Minima in the generalized oscillator strength (GOS) and the convergence of the GOS to the first Born approximation (FBA) limit for the Ba 6s 1S→6p 1P optically allowed transition are investigated. The random-phase approximation with exchange, which takes into account correlation effects among the atomic electrons themselves, and the convergent close-coupling (CCC) approximation are used for the calculations. We find the following. (1) The GOS as a function of the momentum transfer squared K2 is characterized by a complex structure of multiple minima, significantly different in the two approximations and approaches the high-energy FBA limit only at small K2 values (less than about 0.5 a.u.). (2) The number of minima calculated in the CCC approximation increases with increase in energy, but does not correspond to the number obtained in the FBA, even at high energy ∼1 keV. The CCC and FBA minima are in general not directly related. The FBA minima, except for the first, do not correspond to physical observables at these energies. (3) At high energy the interaction between the incident electron and the target remains significant, resulting in slowing down the convergence of the CCC GOS to the corresponding nonrelativistic FBA results

Fine structure levels of Cl V and their lifetimes

We report a large scale configuration interaction calculation of Cl V by taking account of relativistic effect through the Breit-Pauli approximation. Excitation energies of the lowest 49 fine structure levels relative to the ground state $3s^23p(^2{\rm P}^o_{1/2})$ are found to be in good agreement with the NIST recommended data. Oscillator strengths, line strengths and radiative rates for the optically allowed and intercombination transitions among these levels and life times for some relatively longer lived fine structure levels are also reported for this ion. We confirm the interesting result that the life times for the multiplets of $3s3p^2(^4{\rm P})$ and $3s3p(^3{\rm P})3d(^4{\rm F})$ are of the order of microseconds

Uniform electromagnetic field as viscous medium for moving particles

The mechanism of transverse radiation viscosity acting on free charges, atomic, and small macroscopic particles in uniform electromagnetic fields is analyzed. It is shown that in the process of light scattering by these particles, besides the force accelerating them in the direction of propagation of the radiation, there is a force in the transverse direction slowing them down. The general expression for this force is obtained. It is considered how this force can influence: (i) the motion of ultrarelativistic electrons in transverse photon fluxes; (ii) the behavior of a beam of nonrelativistic electrons moving in a copropagating uniform electromagnetic field; (iii) the transverse motion of atoms under the action of resonant radiation and (iv) the motion of small macroscopic particles