Identification of slowly diffusing metastable states of the nitrogen molecule

Experiments [Haydon et al., Chem. Phys. 206 (1996) 245.] have confirmed the existence of a slowly diffusing metastable state of the nitrogen molecule in addition to the well-known A(3) Sigma u(+) state. The second state is populated in prebreakdown discharges and is characterized by a coefficient for diffusion through ground-state nitrogen of about one quarter of that of the A(3) Sigma(u)(+) state. Recent experimental work on the structure of the nitrogen molecule provides much evidence bearing on the question of the nature of the second slowly diffusing state. Examination of a wide variety of possible candidates leads to the conclusion that, on presently available evidence, this state is most likely to be a highly vibrationally excited X(1) Sigma(g)(+) state.