Microwave Spectrum of CFCl3

A calculation has been made for the hyperfine spectrum of the J = 1→2 transition for symmetric‐top molecules having three identical nuclei of spin $\frac{3}{2}$ . Measurements on the J = 1→2 through J = 6→7 transitions of CFCl₃ are described and the results are used to determine the molecular structure, the quadrupole coupling constant with respect to the molecular symmetry axis, and the centrifugal distortion coefficients. The J = 1→2 transition of CHCl₃ has been measured and the results are compared with those for CFCl₃ and with previous work on CHCl₃.