Isotope shift studies of the high-pressure carbon bands

High-pressure carbon bands have been excited in condensed discharges through CO containing about 40% enriched 13C and photographed on a 3.4-m Ebert grating spectrograph. The isotope shifts, ν 12C2–ν′ 12C13C, measured for the bands at 4368.8, 4680.2, 5899.3, and 6442.3 Å, agree with those calculated on the assumption that the bands arise from an initial level of ν′ = 6 and involve the 6–4, 6–5, 6–8, and 6–9 transitions of the A3Πg–X′ 3Πu system of C2.