HIGH-NP RYDBERG STATES OF ATOMIC CARBON STUDIED THROUGH VUV AND UV DOUBLE-RESONANCE

We report on the use of an efficient stepwise-resonant two-photon exci tation scheme to study high principal quantum number even-parity (2pnp ) Rydberg states of atomic carbon. This scheme uses intense vacuum ult raviolet light to drive the resonance transition of the atoms, followe d by excitation to Rydberg states with tunable ultraviolet light. Atom ic carbon was produced under high vacuum conditions using laser ablati on. Analysis of the spectrum of the unperturbed J=3 Rydberg series bel ow and above the first ionization limit yielded a new value for the io nization potential of the atom, with an accuracy primarily limited by the accuracy with which the intermediate state energy is known. The sp ectra of the J=0, 1, and 2 Rydberg states all displayed the effects of coupling between different series converging to the two fine-structur e states of the ion core. These spectra have been successfully reprodu ced using ab initio R-matrix calculations. [S1050-2947(98)09011-8].