LOW VIBRATIONAL LEVELS OF THE IONIC-COVALENT COUPLED-STATE AO(+) OF NAI AND ITS POTENTIAL FUNCTION

The A0(+) state of NaI was investigated towards the minimum of its potential using laser-induced fluorescence and Lambda-type double resonance spectroscopy via the covalent CO+ state, because significantly different potential functions were proposed in the literature due to missing spectroscopic data. The vibrational interval upsilon(adia) = 135-282 measured previously by Schaefer et al. was extended to vibrational levels as low as upsilon(adia) = 40 Transitions to lower levels are masked by the very strong CO+-B1 transition. An improved potential curve for A0(+) was derived. The uncertainty by the unknown lowest vibrational levels is discussed. A comparison of the new curve with others reported in the literature is given.