Abstract
A Fermi coupling constant of about 35 cm-1 has been found between both pairs of bands (ν 1, 2ν 5 0) and (ν 1 + ν 6 ±1, 2ν 5 0 + ν 6 ±1) through the analysis of the centres of these four bands. This result has been confirmed by the study of the pair of bands (ν 1 + ν 2, ν 2 + 2ν 5 0).