Study of the 71Π u state of sodium dimer by polarisation labelling spectroscopy

Two-colour polarisation labelling experiment measuring excitation spectra of Na2 in the spectral range 34, 600−39, 400 cm−1 has furnished observation of the previously unknown 71Piu 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 Te = 36583.86 ± 0.03 cm−1, ωe = 107.50 ± 0.03 cm−1 and Re = 3.640 ± 0.001 Å.