Knowledge Bank

Time-resolved fluorescence-detected infrared-ultraviolet optical double resonance (IR-UV DR) experiments have been. used to obtain detailed measurements of spectroscopic and dynamical processes in the $\nu_{CC} + 3\nu_{CH}$^{\prime\prime} region of acetylene ($C_{2}H_{2}$) at 11 $600 cm^{-1}$. The rotational energy transfer (RET) and vibrational energy transfer (RET) and vibrational energy transfer (V-V) kinetic data collected have already been well fit to 3 detailed rate-equation model that incorporates empirical exponential -gap fitting $laws.^{h}$ In order to explain some of the unusual effects observed in this region we now use the cluster/polyad model that has already successfully interpreted the vibrational energy pattern in $C_{2}H_{2}$ up to $12 000 cm^{-1}.^{i}$ Our work emphasises rotational perturbations, after including the rotational l-type resonance interaction. This enables us to identify the intramolecular couplings responsible for enhancement of rotationally-resolved V-V energy transfer between coupled rovibrational levels of the $\nu CC+3\nu CH$^{\prime\prime} manifold. The model also provides qualitative evidence that Coriolis-type perturbations are responsible for other unusual symmetry-breaking phenomena in this region.