High-resolution jet-cooled spectroscopy of SF6: The nu(2)+nu(6) combination band of (SF6)-S-32 and the nu(3) band of the rare isotopomers

The Fourier transform infrared spectrum of SF6 was recorded in a supersonic expansion jet of an SF6/argon mixture. The SF6:Ar seeding ratio was 2:3. T he instrumental bandwidth was 0.005 cm(-1). A globar source and an MCT dete ctor were used. A rotational temperature of approximately 30 K was achieved . The nu(2) + nu(6) combination band of (SF6)-S-32 was analyzed using a mod ified version of the spherical top data system (STDS) programs developed in Dijon. Avery good fit was obtained for this band with an rms of 0.0036 cm( -1). The effective Hamiltonian was developed up to fourth order for the ups ilon(2) + upsilon(6) part, to second order for the nu(2) and ground state p arts, and to first order for the nu(6) part. Five hundred twenty-one transi tions were assigned, 40 of them reaching the F-2u forbidden sublevel. The p ositions of the two F-1u and F-2u sublevels are found to be 991.276 and 989 .487 cm(-1), respectively. The upsilon(3) band of the (SF6)-S-33 and (SF6)- S-34 isotopomers were also analyzed. Parameters and simulations are present ed. A first detection of the nu(3) Q branch of (SF6)-S-36 (0.02% natural ab undance) is reported. (C) 1998 Academic Press.