Optical Spectroscopy of High-$L$ Rydberg States of Calcium

The Resonant Excitation Stark Ionization Spectroscopy (RESIS) technique has been used to measure the details of the binding energies of a non-penetrating high-$L$ Rydberg electron bound to the Ca$^{+}$ ion. A sample of high-$L$ Rydberg calcium atoms is formed by capture of a single electron from an $n = 9$ rubidium Rydberg target by a fast beam of Ca$^{+}$ ions. Individual fine-structure levels in the $n = 10$ manifold of Ca are selectively detected using Doppler-tuned CO$_{2}$ laser excitation to $n = 26$, followed by Stark ionization of the $n = 26$ products. The Stark ionization rate is proportional to the population of the individual $L$ level which is selectively excited by the CO$_{2}$ laser and the positions of these lines are used to determine initial estimates of the dipole and quadrupole polarizabilities of the Ca$^{+}$ ion.