NEW STUDY OF THE EVEN-PARITY SPECTRUM OF CA-I AND OF THE INFLUENCE OF COLLISIONS ON HIGH RYDBERG STATES

A new study of the even-parity spectrum of Ca I is reported. The term assignments of the 3d2 doubly excited configuration are discussed in relation to those of the isoelectronic sequence and to the corresponding assignments in Ti I. The significance of term-dependent contraction of the 3d orbitals in Ca I, not considered in earlier studies of this spectrum, is demonstrated from ab initio Hartree-Fock calculations, and the energies of the missing terms are estimated. The authors show that data for the members n=62 to 85 of 4snd 1D2 do not agree as well as originally surmised with earlier MQDT extrapolations, indicating the presence of a further perturbation. They have investigated the breakdown of the Delta J selection rule in the presence of collisions with a foreign gas. A collision-induced perturbation around n=63 of 4snd 1D2 is used to locate the missing 1G4 term of 3d2. © 1990, IOP Publishing Ltd.