On the complexity of the absorption spectrum of molecular nitrogen

The spectral properties of molecular nitrogen are crucial to a better understanding of radiative-transfer phenomena and activated N/N2 chemistry in the Earth's upper atmosphere. Excited states of N2 are difficult to access experimentally, and analysis of its electric dipole-allowed spectrum is notoriously complex. In this paper, we give an overview of these complexities and of the power of extreme ultraviolet ionization spectroscopy in unraveling many of the observed features. Some illustrative examples from our own research will be discussed.