Observation of Na2 Rydberg states and autoionization resonances by high resolution all-optical triple resonance spectroscopy

Na2 Rydberg states have been observed for 10 ⩽ n ⩽ 119 and 0 ⩽ J ⩽ 9 using high resolution all-optical triple resonance spectroscopy and an ultrasensitive ionization detector. This represents the first example of high resolution triply resonant photoionization with cw lasers in any molecule. An improved ionization potential of Na2 was estimated by extrapolation to be IP = 39478.75 ± 0.04 cm−1, corresponding to an improved molecular ion dissociation energy De = 7973.83 ± 0.12 cm−1. Four series, np 1∑u+, np 1Πu, nf 1∑u+ and nf 1 Πu, were found and rovibrational interactions, l uncoupling, stroboscopic effects and Fano autoionization profiles were observed in the spectra.