Spectrally resolved UV absorption cross-sections between 190 and 320 run were measured in shock-heated CO, between 880 and 3050 K and H2O between 1230 and 2860 K. Absorption spectra were acquired with 10 mus 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 CO, is transparent (sigma < 10(-22) cm(2)) at wavelengths longer than 200 nm, hot CO2 has significant absorption (sigma > 10(-20) cm(2)) extending to wavelengths longer than 300 nm, The temperature dependence of CO, absorption strongly Suggests sharply increased transition probabilities from excited vibrational levels. (C) 2002 Published by Elsevier Science B.V.