High-resolution spectroscopy of propargyl radical

The high resolution infrared spectrum of the $\nu\sb1$ acetylenic CH stretch of the propargyl radical H$\sb2$CC$\equiv$CH has been obtained by the color center laser kinetic spectroscopy method. The propargyl radical is produced by flash photolyzing stable precursors propargyl bromide or propargyl chloride using the ArF excimer laser. The transient infrared absorptions of the propargyl radical are probed by the color center laser. More than 300 absorption lines were observed in the frequency region of 3304 cm$\sp{-1}$ to 3337.5 cm$\sp{-1}.$ Most of these lines were assigned to the different K subbands of the $\nu\sb1$ fundamental vibrational mode except those lines belonging to an unknown hot band. The upper state energies were obtained by adding the ground state energies appropriately to each observed P and R transitions. Then these upper state energies were fitted by a least squares fitting program and the upper state rotational constants A, B, C and centrifugal distortion constants $\rm\Delta\sb{K},\ \Delta\sb{NK}$ and $\rm\Delta\sb{N}$ together with the band origin $\nu\sb1$ were obtained from the fitting. K = 2$\pm$ sublevels were found perturbed by another vibrational mode so they were not used in the fitting. The nature of this perturbation was recognized as a Coriolis interaction