High-Resolution Infrared Diode Laser Spectroscopy of X²Π CCl¹

The high-resolution transient infrared spectrum of X²Π CCl near 12.2 μm was measured by diode laser absorption spectroscopy following 193 nm excimer laser photolysis of CHClBr₂. Many lines in the v = 1-0, 2 ← 1, 3-2, 4-3, and 5-4 bands for C³⁵Cl were identified in addition to lines in the first four of these vibrational bands for C³⁷Cl. The new data were combined in a least squares fit to all the available high resolution infrared data, and combination differences from the electronic spectrum of the radical, including both chlorine isotopes simultaneously. The equilibrium molecular parameters so determined are more complete than previously available and should reliably predict higher vibrational bands. The results were used to estimate a potential curve for the radical, from the Rydberg-Klein-Rees procedure, and fits to the data for the individual isotopes allowed a separation of the spin-rotation and centrifugal distortion of the spin-orbit fine structure terms.