Many properties of solid (and liquid) nitrogen are reviewed very thoroughly in an article by T.A. Scott ; the most important characteristics are briefly reviewed here.
The isolated nitrogen molecule N2 has dimensions, defined by the surface enclosing 95% of the electron density, of about 3.39 Å diameter 4.34Å in length. Spectroscopic studies of the vibrational (stretch) modes of the molecule indicate that in the condensed states the molecule is slightly distorted by interactions with neighbouring molecules.
Nitrogen exists as two stable isotopes - 99.63% is 14N with nuclear spin 1 and 0.37% is 15N with spin 1/2. With such a small fraction of 15N2 the properties of solid, natural N2 and solid pure 14N2 are virtually indistinguishable.