Collisional quenching of vibrationally excited azabenzenes by unexcited azabenzenes

The collisional quenching of vibrationally excited methyl-substituted azabenzene series (pyrazine, pyridine, and pyrimidine), and deuterated species by unexcited parent molecules was studied with time-resolved C–H (or C–D) stretching infrared fluorescence spectroscopy. The collisional quenching rate and the average energy loss per collision were measured, showing an increase as the number of methyl groups and the dipole moment increase. The results indicate that the vibration-to-vibration energy transfer mediated through the dipole–dipole attractive force plays an important role in the collisional quenching of azabenzenes. The internal rotation of the methyl group facilitates the quenching of the methyl-substituted azabenzenes.