Anisotropic interactions in autoionizing Rydberg systems

We present an improved theoretical description of Rydberg electron motion in the presence of an arbitrary ionic core. Through the use of a generalized eigenvalue equation involving Coulomb, multipole, and polariza tion interactions we are able to describe accurately the physics of the autoionizing Mg 3pnf Rydberg states. The vector hyperpolarizability beta(v), the proportionality constant for an interaction term with the operator structure <(L)over right arrow (c)>.<(l)over right arrow /r(6)>, where <(L)over right arrow (c)> and (l) over right arrow are the orbital momenta of the ionic core and the Rydberg electron, is found to be 1.885 a.u., roughly two orders of magnitude larger than in ground-state Ne+. The effects of nonadiabatic radial interactions now emerge clearly. Comparisons with measured autoionization energies and rates, and with those computed using R-matrix and multichannel quantum defect theory methods, confirm the accuracy of this approach; The concept of adiabatic torquing of orbital planes is introduced and explored in Rydberg magnesium.