Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 18: Photoionisation II (joint session A and MO)

A 18.9: Vortrag

Freitag, 6. April 2001, 17:45–18:00, H1012

Invariant Technique in the Theory of Angular Distributions

in Atomic Processes with Polarized Particles

— •Nikolai L. Manakov¹, Alexei V. Meremianin¹, and Anthony F. Starace² — ¹Department of Physics, Voronezh State University, 394693 Voronezh, Russia — ²Department of Physics and Astronomy, The University of Nebraska, Lincoln, NE 68588-0111, USA

Separation of kinematical (i.e., dependent on the geometry, polarizations and momentum directions of the target and projectiles) and dynamical factors is the major problem in an analysis of angular distributions. We develop a general method for the parametrization of cross sections in terms of simple vector constructions, such as the scalar products of vectors inherent to the concrete problem and/or expansions in Legendre polynomials of angles between these vectors. The key idea of this method is to avoid the direct use of standard techniques of angular momenta algebra which require tedious routine calculations. In general, our approach is based on an invariant (i.e., independent of a concrete coordinate frame) analysis of the fundamental objects of angular momentum theory, irreducible tensor operators T_jm, using invariant representations of finite rotation matrices. In addition, we use the multipole expansions of tensor functions T_jm dependent on vector parameters and also reduction techniques for the tensor products of spherical harmonics.

We illustrate details of the method by analyzing of beyond electric-dipole-approximation effects on the polarization and angular dependences of photoprocesses in the VUV- and X-ray regions.