Abstract
N+2 is one of the main ions in ionosphere of planets and moons such as Earth or Titan. Experimentally obtained data are not very consistent, as they differ by a factor of 2-3. The theory [Little et al] suggests, the problem is in the different rates of recombination for different vibrational states, which seems to be the main reason for the inconsistency. In different experiments were different vibrational populations
[Sheehan et al]. We have performed measurements of recombination coefficient of N+2 ions with electrons using stationary afterglow apparatus with Cavity Ring-Down Spectroscopy and microwave diagnostics in temperature scale 150-250 K. We probed in situ the number densities of both ground and the first excited vibrational states of N+2 . The population of the higher state is around 2%, therefore our data are appropriate for the ground vibrational state.