Optical-optical double resonance spectroscopy of theΣg+1‘‘shelf’’ states andΠg1states ofNa2using an ultrasensitive ionization detector

Using a shielded cylindrical space-charge-limited diode ionization detector and optical-optical double resonance, the exotic potential energy curves of the 3, 4, 5, and 6 ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{\mathit{g}}^{+}{}_{}{}^{}$ ‘‘shelf’’ states and 2 and 3 ${}_{}{}^1{}_{}{}^{}\mathrm{\Pi }_{\mathit{g}}^{}{}_{}{}^{}$ states of ${\mathrm{Na}}_2$ have been extensively studied including levels near dissociation (>99.8% of well depth) with very large outer classical turning points, and long range avoided crossings giving rise to potential ‘‘shelfs.’’ The long range potential can all be understood and also provide stringently tested high quality theoretical calculations of highly excited states.