Temperature measurements of shock waves and detonations by spectrum-line reversal III. Observations with chromium lines

Abstract

Temperature measurements have been made with the chromium resonance triplet at 4254, 4274 and 4289 Å, controlled amounts of chromium being introduced in the form of the volatile carbonyl; this method has the advantage that it can be used with explosive mixtures. Measurements of vibrational relaxation time have been made for carbon monoxide between 2200 and 2700°K and of the rate of dissociation of hydrogen in hydrogen + argon mixtures between 2400 and 2800°K. Temperature irregularities in the fronts of shocks through argon or neon are discussed, but no satisfactory explanation for them has been found. Excitation processes in monatomic gases are also examined. The method has been used to study the temperature distribution behind detonations which have been initiated by shocks of various strengths. For ethylene + oxygen detonations the chromium excitation temperature is very high at the front; this is attributed to chemiluminescent excitation in the reaction zone. In carbon monoxide + oxygen detonations initiated by weak shock waves we have observed interesting steps in the temperature behind the front and have explained these as being due to delayed ignition behind the shock and an acceleration of the front leading to detonation after the front has travelled some way along the shock tube.