Anticrossing effects in Rydberg states of lithium in the presence of parallel magnetic and electric fields.

Abstract

Rydberg states in lithium have been excited from the ground state by absorption of \ensuremath{\pi}-polarized photons in the presence of parallel electric F and magnetic B fields. The magnetic field strength (B=3.11 T) is high enough to reach the inter-n-mixing regime, and a small electric field strength (F\ensuremath{\simeq}25 V/cm) is sufficient for the lowest state of the n=30 manifold to penetrate into the high-energy part of the n=29 manifold. The first anticrossing is thoroughly studied. Away from the anticrossing the spectrum exhibits two lines, but at the anticrossing a third component appears in the structure in the same energy range. This provides an experimental confirmation for the existence of pairs of almost-degenerate states with opposite parities in the high-energy part of the diamagnetic manifold of lithium. The two components of this doublet behave differently at the anticrossing. The experimental data have been interpreted in a global treatment in which core effects and intermanifold couplings are simultaneously taken into account. The different behavior of low- and high-lying states of the multiplet with respect to these two interactions is analyzed in detail.