New infrared absorption bands of sodium vapor

Abstract

We have seen a new region of absorption in saturated sodium vapor in the infrared region of the spectrum (0.83–2.5 μ). The absorption from 0.83 to 1.18 μ may be the analog of the ultraviolet emission continuum of H₂, possibly arising from the sodium dimer (³Σ_u⁺→³Σ_g⁺) transition, along with contributions from higher sodium polymers. Absorption at longer wavelength is most likely due to higher polymers of sodium (Na₃, Na₄,...).