Knowledge Bank

The collision relaxation cross section of highly vibrationally excited SO$2$ at energies around 45,000 $cm\backslash -1$, which is just below the dissociation limit, has been measured for several $\backslash testitsingle$, highly vibrationally excited levels. The measurement was conducted on rotationally cooled SO$2$ in supersonic jet condition using quantum beat spectroscopy. Quantum beat in laser induced fluorescence from the $C$ state is due to vibronic coupling between zero-order rovibronic levels of $C$ and $X$ states and can be analyzed to give the decay rate constants of the high vibrational levels of the $X$ state. It is found that the collision relaxation cross section of the single highly vibrationally excited level shows a strong correlation with the corresponding vibronic coupling matrix element, likely reflecting that the part of the vibrational character of the single high vibrational level that gives a larger coupling with the $C$ state also provide a stronger transition dipole moment contribution to its collision relaxation.