First observation of the 3ν1+2ν3-ν3 band of 16O3:: problem of consistency between cold and hot band intensities

The 3nu(1)+2nu(3)-nu(3) band of O-16(3) has been observed for the first time below the residual of all the known absorbing bands in the 4100 cm(-1) region. The rovibrational transitions have been assigned for J and K-a up to 31 and 11, respectively, leading to a root-mean-square (RMS) deviation of 2.3x10(-3) cm(-1). The observed line intensities are reproduced with a RMS deviation of 10%, which is very satisfactory bearing in mind the weakness of this band. The problem of consistency of the intensity of the cold-to-hot band extrapolation and of the effects of anharmonic resonances with distant partners on transition moment parameters is discussed. This work clearly shows the necessity to account for strong anharmonic coupling between distant vibrational states in order to be theoretically consistent.