Microwave spectra of nitrogen trifluoride in the excited vibrational states: Equilibrium structure

Abstract

The microwave spectra of two isotopic species of the NF 3 molecule were investigated in the excited vibrational states. The vibration-rotation interaction constants α v B for the ν 1, ν 2, ν 3 and ν 4 states were found to be −43.45, +38.65, +78.81, and +4.48 MHz for 14NF 3 and −38.41, +40.14, +75.67, and +4.64 MHz for 15NF 3, respectively. The equilibrium rotational constant, B e , was then derived to be 10761.9 1 ± 0.2 MHz for 14NF 3 and 10710.6 3 ± 0.2 MHz for 15NF 3, from which the equilibrium structure was determined to be r e (N-F) = 1.365 ± 0.002 A ̊ and α e (∠FNF) = 102°22′ ± 2′. A set of linear relations was derived between cubic potential constants from the observed α v B and ℓ-type doubling constants.