Fig. 3: Experimental line centres vs database values for carbon dioxide.
From: Optical frequency metrology in the bending modes region

a Difference between experimental and high-resolution transmission molecular absorption database (HITRAN33) line centres for several lines of the R branch of the v2 band and b of the Q branch of the v1 ← v2 band. Error bars represent standard errors of the mean (±1σ). The variation of error bars comes from a different number of measurements per line.