Hyperfine Structure in the Microwave Spectra of CFCl3 and CHCl3

Abstract

The theory for the hyperfine structure in the rotational spectrum of symmetric‐top molecules containing three identical quadrupolar nuclei is discussed. Formulas and tables are given from which the quadrupole interaction energies, and the transition frequencies and intensities can be calculated for the case of nuclear spin $\frac{3}{2}$ . The theory is applied to the molecules CF³⁵Cl₃ and CH³⁵Cl₃ with completely satisfactory results. The bond‐axis quadrupole coupling constants determined for CF³⁵Cl₃ and CH³⁵Cl₃ are −79.9±0.6 Mc/sec and −77.9±0.5 Mc/sec, respectively. Rotational constants were determined for four rotational transitions of each molecule, and the results are in agreement with centrifugal‐distortion theory.