Quenching of Rydberg states by atoms with small electron affinities

We discuss the theory of quenching of Rydberg slates by atoms with small el ectron affinities and perform calculations for quenching of s and d states of Ne by Ca. There are two contributions to the quenching cross section: th e ion-covalent coupling contribution, which is due to the formation of an i ntermediate ionic state, and the impulse contribution. The first is very se nsitive to the electron affinity of the projectile and may be used for stud ies of weakly bound anions. The ion-covalent coupling contribution is domin ant for the process of quenching of Rydberg states with large quanturn defe cts (e.g. s states) at relatively low principal quantum number n, whereas t he impulse contribution dominates the process of quenching of states with s mall quantum defects (e.g. d states of Ne). We present calculations of quen ching of s stares by Yb atoms with a hypothetical electron affinity of 2 tn eV and show that experimental studies of quenching of Rydberg states by Yb might help in determining the electron affinity of Yb even if it is negativ e. In the latter case the quenching cross section as a function of n should exhibit oscillations (Borodin V M and Kazansky A K 1992 J. Phys. B: At. mo l. Opt. Phys. 25 971).