RESONANTLY ENHANCED NS AND ND RYDBERG SPECTROSCOPY OF SODIUM

We report new observations of photodissociation and ionization in sodi um vapour by using a Nd:YAG pumped dye laser and a thermionic diode as an ion detector employing two experimental geometries. In the first e xperiment, single photon dissociation of a sodium dimer into an excite d atomic state followed by a one-photon excitation to even parity Rydb erg states of atomic sodium has been investigated. In the second arran gement, we used a two-colour two-step excitation process which yields much higher Rydberg members of the even parity ns S-2(1/2) and nd D-2( 3/2.5/2) series. The relative intensities of the ns and lid members of the Rydberg series are attributed to the spatial overlap between the 3p and Ils and rid wavefunctions, evidenced by the ab initio single co nfiguration Hartree-Fock calculations.