The high-lying vibrational levels and dissociation energy of the a(3)Sigma(+)(u) State of Li-7(2)

Perturbation-facilitated optical-optical double resonance (PFOODR) has been used to access the 2(3)Pi(g) state of Li-7(2) via the X(1)Sigma(g)(+) --> (A(1)Sigma(u)(+) similar to b(3)Pi(u)) --> 2(3)Pi(g) excitation scheme usin g two single-mode tunable lasers. The selected (A(1)Sigma(u)(+) similar to b(3)Pi(u)) mixed level provides a gateway through which the triplet manifol d can be accessed. Fluorescence from single rovibrational levels of 2(3)Pi( g) to the a(3)Sigma(u)(+) state was detected at high resolution using a Fou rier transform spectrometer. Transitions to v = 0-9 in the a(3)Sigma(u)(+) state were observed, covering the potential well almost to the dissociation limit. The data were analyzed using a near dissociation expansion (NDE) te chnique and the resulting vibrational and rotational parameters were used t o calculate a new RKR potential curve which reproduced the observed energy levels to within a rms error of 0.02 cm(-1). The following parameters were obtained for the a(3)Sigma(u)(+) state: D-0 = 301.829 +/-. 0.015 cm(-1), D- e = 333.69 +/- 0.10 cm(-1), T-e = 8183.12 +/- 0.12 cm(-1) (C) 1999 Academic Press.