Ultraviolet absorption spectra of shock-heated carbon dioxide and water between 900 and 3050 K

Spectrally resolved UV absorption cross-sections between 190 and 320 nm were measured in shock-heated CO2 between 880 and 3050 K and H2O between 1230 and 2860 K. Absorption spectra were acquired with 10 μs time resolution using a unique kinetic spectrograph, thereby enabling comparisons with time-dependent chemical kinetic modeling of post-shock thermal decomposition and chemical reactions. Although room temperature CO2 is transparent (σ<10−22 cm2) at wavelengths longer than 200 nm, hot CO2 has significant absorption (σ>10−20 cm2) extending to wavelengths longer than 300 nm. The temperature dependence of CO2 absorption strongly suggests sharply increased transition probabilities from excited vibrational levels.