The Infrared Spectra of NF3 and PF3

The infrared spectra of NF3 and PF3 have been investigated with a prism instrument in the range 250 cm−1 to 5000 cm−1. The fundamental frequencies are for NF3, ν1(A1)=1032 cm−1, ν2(A1)=647 cm−1, ν3(E)=905 cm−1, and ν4(E)=493 cm−1; and for PF3, ν1(A1)=892 cm−1, ν2(A1)=487 cm−1, ν3(E)=860 cm−1, and ν4(E)=344 cm−1. Force constants as well as thermodynamic functions are calculated for both molecules.