Lucien Doyennette

Temperature dependence of the diffusion and accommodation coefficients in nitrous oxide and carbon dioxide excited into the (00°1) vibrational level

We have studied the temperature dependence of the relaxation rates in nitrous oxide and carbon dioxide excited into the (00°1) level by absorption of the radiation of a Q‐switched laser. The relaxation constant β has been determined by measuring the decay time of the fluorescence emitted by the gas. Measurements were performed in the temperature range between room temperature up to 1000 °K and at gas pressures low enough to determine the diffusion coefficient of the excited molecules and their wall‐deexcitation probability versus temperature.

Vibrational energy transfer from the (00°1) level of 14N2O and 12CO2 to the (m, nl, 1) levels of these molecules and of their isotopic species

We have studied versus temperature the fast vibvrational energy transfers which occur between two nitrous oxide molecules, or two carbon dioxide molecules, initially excited by a laser pulse into the (00°1) level. These transfers occur upon near−resonant collisions of the type M(m, nl, 1) + M(m′, n′l′, 0) ? M(m, nl, 0) + M(m′, n′l′, 1) with M = 14N2O) or 12CO2. The rates of these V−V transfers have been measured from room temperature up to 900 K by the laser−induced fluorescence method. These exchanges can play an important role in the kinetics of the fast V−V transfers which occur in gaseous mixtures involving these molecules. This is particularly the case for the transfers occurring between different isotopic species of CO2 and N2O, such as 12CO2−13CO2, and mixtures of 14N2O with 14N15NO, 15N14NO, and 15N2O, also studied in this work. The transfer rates for the isotopic mixtures of nitrous oxide have been measured versus temperature. The experimental results are compared with the values calculated on th...

Temperature dependence of the vibrational relaxation of CO (v=1) by NO, O2, and D2, and of the self‐relaxation of D2

Rate constants for the vibrational de‐excitation of CO(v=1) by NO, O2, and D2 have been measured as a function of the temperature using the laser‐induced vibrational fluorescence technique. In the temperature range from 100 to 700 K considered in our experiments, far‐from‐resonance V–V energy transfers occur between CO and the collision partners. In CO–NO and CO–O2 samples, the CO fluorescence decay curves are single exponentials; only the total de‐excitation rates χCO–M=kCO–M+kMCO of CO(v=1) by M=NO or O2 may be experimentally deduced, kCO–M being V–V transfer rate and kCOM the V–TR de‐excitation rate. In the CO–D2 system, the fluorescence exhibits a double exponential decay; the V–V transfer rate kCO–D2 is found to be much greater than the V–TR de‐excitation rate kCOD2, and the self‐relaxation rate kD2 of deuterium has also been deduced from measurements. The V–V transfer rates kCO–M calculated from a semiclassical method derived from that of Shin, and using a Morse potential, have been compared to the ...

Vibrational energy transfers from the v=1 level of HBr, HCl, and DF to the v=1 level of CO, NO, N2, and to the 0001 level of CO2 and N2O: A rate constant calculation based upon long‐range multipolar forces

Rate constants for far‐from‐resonance V–V transfers in HX–M and DF–M systems, with X=Cl and Br and M=CO, NO, N2, CO2, and N2O, have been calculated from the semiclassical method of Dillon and Stephenson: the transfer probability is calculated from an exponential form of the scattering operator, and long‐range multipolar forces are assumed, involving not only interactions between vibrational transition moments but also interactions between permanent moments, the effect of which is to make the multiquanta rotational transitions efficient. The formalism, developed by these authors for HX–CO2 systems, i.e., for the case of a dipole–dipole vibrational interaction and a dipole–quadrupole rotational interaction, has been extended to other cases involving a dipole–quadrupole vibrational interaction or a dipole–dipole rotational interaction, in order to treat systems such as HX–N2 or HX–N2O systems. The computations have been performed for temperatures between 300 and 900 K. The comparison between calculated and experimental values shows that, as expected from the analysis of the experimental results, long‐range multipolar forces play certainly a preponderant role in these transfers, all the more as the temperature is lower. The limits of the model are discussed.