The reaction between H2 and D2 in a shock tube: Study of the atomic vs molecular mechanism by atomic resonance absorption spectrometry
- 15 September 1977
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 67 (6) , 2803-2810
- https://doi.org/10.1063/1.435199
Abstract
The exchange reaction between hydrogen and deuterium was studied behind reflected shocks in a single pulse shock tube. A vacuum uv monochromator and a Lyman‐α radiation source were attached to the end block of the driven section in order to determine the hydrogen atom profile during the hot phase. These atoms are the result of impurities which are present in the shock tube. Two calibration attempts of the It/I0 vs [H]t around 1250 °K, using the decomposition scheme of propane and the postexplosion conditions in H2/O2/Ar mixtures, were unsuccessful. A calibration method which utilizes an integrated absorption profile is described. A two parameter calibration function (modified Beer–Lambert law) was derived: It/I0=exp(−α[H]βt), where α=2.92×107 and β=0.73 in units of mole‐cm. For each test, a sample was withdrawn from the tube and was analyzed mass spectrometrically for postshock distribution of product and reactants. In addition, the absorption profile at 1215.7 Å was recorded and the extent of HD produced by hydrogen atoms (which originated from impurities) was numerically integrated using the two parameter calibration function and the atomic chain reactions H+D2→HD+D and D+H2→HD+H. The mass spectrometrically measured extents of exchange were always considerably higher than the ones calculated from the absorption profile, on the average by a factor of 2–3. If the difference between the two conversions is attributed to a molecular mechanism, then if calculated on the basis of the rate law H2+D2→2HD the following rate constant is obtained: k6=1014.1±0.8 exp[−(38±5) ×103/RT] mole−1 cm3 sec−1.Keywords
This publication has 28 references indexed in Scilit:
- Kinetics of the Homogeneous Exchange Reaction: NH3 +D2→NH2D +HD. Single-Pulse Shock-Tube StudiesThe Journal of Chemical Physics, 1970
- Isotope Exchange Rates. VII. The Homogeneous Atom Switching Reaction between Oxygen MoleculesJournal of the American Chemical Society, 1969
- The Role of Vibrational, Excitation in the Formation of 4‐Center Transition StatesIsrael Journal of Chemistry, 1969
- Isotope Exchange Rates. V. The Homogeneous Reaction between H2S and D2The Journal of Chemical Physics, 1968
- Further Studies on the Homogeneous Exchange Reaction H2 + D2The Journal of Chemical Physics, 1967
- Isotope Exchange Rates. III. The Homogeneous Four-Center Reaction H2+D2The Journal of Chemical Physics, 1966
- Isotope Exchange Rates. IV. The Homogeneous Reaction Between CH4 and D2The Journal of Chemical Physics, 1966
- Studies with a Single-Pulse Shock Tube. I. The Cis—Trans Isomerization of Butene-2The Journal of Chemical Physics, 1963
- 6. The thermal interaction of deuterium and ammoniaJournal of the Chemical Society, 1936
- Experiments on heavy hydrogen - V—The elementary reactions of light and heavy hydrogen. The thermal conversion of ortho-deuterium and the interaction of hydrogen and deuteriumProceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1935