Rotational analysis of the ν1 band of trichlorofluoromethane from high resolution Fourier transform and diode laser spectra of supersonic jets and isotopically enriched samples

Abstract

The spectrum of CCl3F (trichlorofluoromethane, CFC 11) has been measured in the region of the ν1 fundamental (1050–1120 cm−1) by high resolution interferometric Fourier-transform spectroscopy [0.004 cm−1 bandwidth full width at half maximum, apodized] and by diode laser spectroscopy (bandwidth 0.0008–0.0020 cm−1 FWHM) at room temperature, in cold cells and in supersonic jet expansions. Fourier-transform infrared and diode laser spectra of isotopically pure C35Cl3F have been recorded at room temperature in static cells. The C35Cl3F spectra allowed an analysis of the rotational structure to be started successfully for the first time. The rotational analysis of the isotopic species C35Cl237ClF and C35Cl37Cl2F, which are asymmetric rotors, was initiated from diode laser spectra of natural CCl3F with a rotational temperature of about 20 K (5% seeded in He) resulting from expansion in a supersonic pulsed slit jet. The rotational analysis yielded effective Hamiltonian constants including accurate band centers for the three most abundant isotopomers C35Cl3F (ν1=1081.2801 cm−1), C35Cl237ClF (ν1=1080.7330 cm−1), and C35Cl37Cl2F (ν1=1080.0663 cm−1), excited state rotational constants, and for C35Cl3F, quartic centrifugal distortion constants. The results are important for and discussed in relation to simulations of atmospheric absorption, line coincidences with CO2 lasers for sub-Doppler spectroscopy, as well as IR multiphoton excitation and infrared laser chemistry.