Anharmonic resonance interactions in the bending manifold associated with ν3 in 13C2D2 studied by high—resolution infrared and Raman spectroscopy

Abstract

The Q branch of the 2ν2 ← ν2 band of 13C2D2 has been recorded with an instrumental resolution of about 0.003 cm−1 using inverse Raman spectroscopy combined with stimulated Raman pumping in order to populate the ν2=1 state. A weak local perturbation evident in the spectrum has been attributed to the effect of an anharmonic resonance between the ν2=2 and ν3=ν4=ν5=1 Σ+ g, states. To study this interaction, the components of the latter vibrational manifold (Σ+ g, − g and Δg), together with all the bending states up to (ν4 + ν5)=2 associated with ν3=1, have been characterized through the analysis of their infrared spectra. Both cold and hot bands from states thermally populated at room temperature, ν4, ν5, 2ν4, 2ν5 and ν4 + ν5, have been recorded in the region between 2300 and 3000 cm−1 at an effective resolution of about 0.009 cm−1. A simultaneous analysis of all the assigned transitions has been performed on the basis of a theoretical model which takes into account the rotational and vibrational ℓ-type resonances within each vibrational manifold, the Darling-Dennison anharmonic resonance between the ν3 + 2ν4 and ν3 + 2ν5 states, and the anharmonic interaction between the 2ν2 and ν3 + ν4 + ν5 states.