THE MICROWAVE SPECTRUM OF DICHLOROFLUOROMETHANE

Abstract

The microwave spectra of C¹²HFCl₂³⁵ and C¹²HFCl³⁵Cl³⁷ have been measured in the frequency range from 10 to 35 Gc/s. Enough R branch and Q branch rotational transitions have been measured in each case to determine the rotational constants A = 6988.73 ± 0.02, B = 3307.25 ± 0.05, and C = 2350.03 ± 0.02 Mc/s for CHFCl₂³⁵ and A = 6943.37 ± 0.05, B = 3219.58 ± 0.04, and C = 2300.57 ± 0.06 Mc/s for CHFCl³⁵Cl³⁷. The out-of-plane coordinate of Cl³⁵ in the symmetric species has been deduced to be 1.4350 ± 0.0006 Å and, if the C–Cl bond length is assumed to be 1.750 ± 0.005 Å, then the Cl–C–Cl angle can be calculated to be 112.2 ± 0.5°. The analysis of the hyperfine structure has led to the values eQV_aa = −41.0 ± 0.2 Mc/s, eQV_bb = +11.37 ± 0.13 Mc/s, and eQV_cc = 29.62 ± 0.13 Mc/s for the diagonal components of the quadrupole coupling tensor along the principal inertial axes. The results are consistent with a cylindrically symmetrical charge distribution around the C–Cl bond and a quadrupole coupling tensor component of eQV_zz = −76.75 Mc/s in the direction of the bond. The only impurity in the sample, obtained from the Matheson Company, seems to have been a trace of HCCF for which the J = 0 → 1 transition has been measured.