One-dimensional N2 gas inside single-walled carbon nanotubes

The unexpected presence of a linear arrangement of co-axially oriented N2 molecules inside aligned single-walled carbon nanotubes is revealed by high resolution near-edge X-ray absorption spectroscopy. The encapsulated N2 molecules exhibit free stretching vibrations with a long electronic lifetime of the X-ray-excited anti-bonding π∗ states. Molecular dynamics simulations confirm that narrow-diameter nanotubes (d < 1 nm) are crucial for stabilizing the linear arrangement of aligned N2 molecules.