The fraction of vibrationally excited CO 2 in the incident beam at high T n was estimated assuming minimal vibrational relaxation in the nozzle. A qualitative confirmation of the same was also obtained using the 3+1 REMPI scheme for CO 2 at 330 nm. Although this scheme is inefficient, it was good enough to observe a systematic increase in the bending (010) state population (relative to the ground state) with increasing T n (SI-4). Based on these measurements we estimate that 26% population is in the excited bending state (010) and 8.5% is in the (020) state, at T n = 853 K. The estimated relative uncertainty in S 0 is about 20% (1σ) and arises mainly from the uncertainties in the incidence beam flux and O-atom coverage measurements. 5.5 x -3 1.8 x -3