Absorption spectrum of CO in the Hopfield helium continuum region: Rydberg bands converging to the X2Σ+ state of CO+ in the region 960–1080 Å

The high resolution absorption spectrum of CO has been reinvestigated in the Hopfield helium continuum region, particularly from 960 to 1080 Å. The Rydberg state 3pπE¹Π was extended to v = 2, and other Rydberg states, $\text{3dσ}{}^3\text{Σ}{}^{\mathrm{+}}$ and F¹Σ⁺, $\text{3dπ}{}^1\text{Π}$, and $\text{4sσ}{}^3\text{Σ}{}^{\mathrm{+}}$ and ¹Σ⁺, which are converging to the X²Σ⁺ ground state of CO⁺, have been identified. The rotational structures of only five bands among the observed ten Rydberg bands have been analyzed.