EFFECT OF HIGH-N AND CONTINUUM EIGENSTATES ON THE STARK-EFFECT OF RESONANCE LINES OF ATOMS AND IONS

We investigate the Stark effect for spectral transitions between low-l ying levels of atoms and ions. We find that often a strong cancellatio n of the shifts of the lower and upper levels occurs, resulting in a s ignificant reduction in the shift. For accurate calculations, therefor e, one has to account for the influence of high-principal-quantum-numb er and continuum levels. As examples, the shifts, splitting, and inten sities of the components of the Li I 2s-2p, Na I 3s-3p, Ba II 5d-6p, B a II 6s-6p, and the quadrupole Ball 6s-5d (shifts only) transitions ar e calculated for electric fields up to approximate to 20 MV/cm. Compar ison of the calculated shift parameters to experimental data for the L i I 2s-2p, Na I 3s-3p, and Ba II 6s-5d lines, available as yet only fo r low fields for which the effect is quadratic, showed an excellent ag reement for most of these lines.