Microwave spectrum of NF 2

About 350 lines in the microwave spectrum of NF ₂ have been measured in various ranges of frequency between 13.0 and 65.2 GHz by using two types of Zeeman effect spectrometers. Complete assignment of all lines has been achieved and, via the general microwave computer program SPINRO, the rotational constants, centrifugal distortion constants, dipole moment, electronic spin-rotation coupling constants, the constants for the coupling of the several nuclear spins with the electron spin and the nitrogen quadrupole coupling constants have all been obtained. By drawing upon the observed vibrational frequencies the average geometry of NF ₂ has been evaluated. Force constants and Coriolis coupling constants have also been derived. The values of the spin coupling constants for N and for F indicate that NF ₂ is a π-radical with the spin density mainly located on nitrogen. The multiplet patterns indicate that the ground electronic state wavefunction is antisymmetric to rotation about the molecular symmetry axis and so, for a π-radical, identifies the ground state as ²B₁ as has previously been assumed for this molecule.