High-Resolution Jet-Cooled Spectroscopy of SF6: The nu2 + nu6 Combination Band of 32SF6 and the nu3 Band of the Rare Isotopomers.

ABSTRACT

The Fourier transform infrared spectrum of SF6 was recorded in a supersonic expansion jet of an SF6/argon mixture. The SF6Ar seeding ratio was 23. The instrumental bandwidth was 0.005 cm-1. A globar source and an MCT detector were used. A rotational temperature of approximately 30 K was achieved. The nu2 + nu6 combination band of 32SF6 was analyzed using a modified version of the spherical top data system (STDS) programs developed in Dijon. A very 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 nu2 + nu6 part, to second order for the nu2 and ground state parts, and to first order for the nu6 part. Five hundred twenty-one transitions were assigned, 40 of them reaching the F2u forbidden sublevel. The positions of the two F1u and F2u sublevels are found to be 991.276 and 989.487 cm-1, respectively. The nu3 band of the 33SF6 and 34SF6 isotopomers were also analyzed. Parameters and simulations are presented. A first detection of the nu3 Q branch of 36SF6 (0.02% natural abundance) is reported. Copyright 1998 Academic Press.