Fourier-transform spectroscopic study of the rotational intensity distribution in the first positive B3Πg–A3Σu+ band system of the nitrogen molecule

Abstract In the present work we have studied the rotational intensity distribution in the 0–0, 0–1 and 1–3 bands of the B 3 Π g –A 3 Σ u + system of N 2 recorded on a Fourier transform spectrometer. The effective Hamiltonian used by Roux et al. (J. Mol. Spectrosc. 97 (1983) 253) for reduction of the experimental line position data to molecular parameters, is found to be adequate in reproducing the observed line intensities. To enhance the accuracy of the theoretical line intensity calculations, it proved necessary to use rotation-dependent Frank–Condon factor. Using the calculated intensities, it was possible to identify certain rotational lines belonging to the weakest branches Q 13 and Q 31 , not reported before.