Reading between the lines:: Exposing underlying features of high resolution infrared spectra (CHClF2)

A technique to facilitate the assignment of congested high resolution IR spectra is presented. It involves subtraction of component spectra simulated from known spectroscopic constants. Application to the v(2) (1313.1 cm(-1)) and v(7) (1351.7 cm(-1)) bands of CHClF2 led to rovibrational line assignments for less intense and overlapping features including the minor isotopomer (CHClF2)-Cl-37 and c-type lines of (CHClF2)-Cl-35. The number of transitions assigned to the fundamental bands increased from 1721 to 6031 for Cl-37, and from 7496 to 9664 for Cl-35, with a greater range of rotational quantum numbers than found in a previous study. A total number of 1457, 484 and 262 line assignments were made for 2(0)(1)9(1)(1), 7(0)(1)9(1)(1) and 2(0)(1)6(1)(1) hotbands respectively, features otherwise completely obscured in the observed spectrum. Rotational and centrifugal distortion parameters were fitted for all the upper states.