Knowledge Bank

The identification of B and C-type Coriolis interactions in the $A~1Au$ state is greatly facilitated by recording double resonance spectra to the vibrationless level of the previously assigned $C~1Ag$ electronic $state1$ of $C2D2$. Analysis of the J and K rotational structure manifest in the double resonance spectra of the $C~$ state allows the identification of B and C-type Coriolis perturbations in the $A~$ state. This analysis can provide direct evidence of the location of the dark $Ag$ and $Bg$ symmetry vibrational states involving $\nu 4,\nu 5$ and $\nu 6$ excitation in the still not fully characterized $A¯1Au$ state of acetylene.