Study of the 7(1)Pi(u) state of sodium dimer by polarisation labelling spectroscopy

Two-colour polarisation labelling experiment measuring excitation spectra of Na-2 in the spectral range 34, 600-39, 400 cm(-1) has furnished observation of the previously unknown 7(1)Pi(u) electronic state. The excited state is characterised by a set of Dunham coefficients describing the f parity levels up to vibrational level v = 28 and the corresponding potential energy curve is constructed by the inverted perturbation approach method. Molecular parameters determined in the fit include T-e=36583.86 +/- 0.03 cm(-1), omega(e)=107.50 +/- 0.03 cm(-1) and R-e = 3.640 +/- 0.001 angstrom.