1ST OBSERVATION OF THE QUASI-BOUND LEVELS AND TUNNELING LINE BROADENING IN THE 3 (1)PI(G) STATE OF NA2 USING AN ULTRASENSITIVE IONIZATION DETECTOR

All quasibound vibrational energy levels v=27 and 28 of the Na2 3 1PI(g) state were accessed by using optical-optical double resonance and detected with a shielded ionization detector. The line broadening due to the tunneling effect was observed to be larger than 1 cm-1 at the rovibrational level v=28, J=31. The potential curve has been determined by the Rydberg-Klein-Rees method and modified using Jeung's calculation for the large distance barrier and comparison of the calculated and the measured line widths. The barrier height was found to be - 126 cm-1 above its asymptotic limit (3s+4p) at 5.98 angstrom. There also exists an unobserved shallow outer well with depth approximately 35 cm-1 at 9.5 angstrom according to our modification of Jeung's calculated potential. One way to possibly probe this outer well is also discussed.