Knowledge Bank

The $A~-X~$ transition of acetylene was the first electronic transition for which a change of point group was confirmed in $detaila$. Previously, harmonic Franck-Condon calculations for this transition were $presentedb$. The present calculations allow for anharmonicity in the ground state, although the upper-state potential is still assumed to be $harmonicc$. The transition moment is taken to be proportional to the $q4\prime \prime$ bending coordinate. For the calculation of the dispersed fluorescence $spectrumd$ it is found that the global potential surface of Halonen, Child and $Cartere$ gives the best qualitative agreement for the intensities, but could be improved for the energies of high bending states.