Kinetics and energy transfer studies using a shock tube and probe laser
A continuous wave infrared CO laser has been used to monitor kinetic processes occurring behind shock waves. Studies have been made of both vibrational energy transfer and reaction kinetics. It has been demonstrated that, following shock-heating, the vibrational levels of CO and DC1 relax via a continuous series of Boltzmann distributions into the final Boltzmann equilibrium distribution at rhe translational temperature. This is shown to be in accord with the established theory, and it is proposed that all diatomic molecules relax in this manner. Previous results for HI, which suggested otherwise, are questioned, and the theoretical arguments used to explain these results are shown to be misconceived. A new method is developed to calculate vibrational relaxation times from any laser absorption trace. The initial vibrational distribution of CO formed in the unimolecular decomposition of OCS at 4000 K has been investigated. It has been found that at least 90 % of the CO is born in the lowest vibrational level v=0, when 50 % would be in v=0 at equilibrium. This result is explained in terms of the dynamics of the reaction. The kinetics of the isotope exchange reaction 12C18O + 13C16>O ⥋ 12C16O + 13C18O have been investigated. The results have been shown to be consistent with an atomic chain mechanism, in conflict with the conclusions of earlier work. Reasons for this are discussed. A general account of the principles of operation of the apparatus is given, and conclusions are arrived at for the most profitable directions of future work.