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One-dimensional N 2 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.