Daniel W. Trainor

Gas phase recombination of hydrogen and deuterium atoms

Rate constants for the reaction H+H+M → H2 + M, with M = H2, He, and Ar were measured over the temperature range 77–298°K. Hydrogen atoms were produced by thermal dissociation and absolute atom concentrations were measured through use of a self‐balancing, isothermal catalytic probe detector. The specific rate constants were 8.1 ± 0.4 × 10−33,u20097.0 ± 0.4 × 10−33, and 9.2 ± 0.6 × 10−33u2009cm6u2009molecules−2 · sec−1 at 298°K for M = H2, He, and Ar, respectively; these values rising to 18.5 ± 2.2 × 10−33,u200912.0 ± 1.5 × 10−33, and 27.4 ± 4.6 × 10−33u2009cm6u2009molecules−2 · sec−1 at 77°K. For the equivalent deuterium atom process with D2 as the third body, the rate constants are 6.1 ± 0.3 × 10−33u2009cm6u2009molecules−2 · sec−1 at 298°K and 15.1 ± 1.0 × 10−33u2009cm6u2009molecules−2 · sec−1 at 77°K. These values are compared with previous experimental measurements and with recent theoretical calculations.

Excitation of ozone formed by recombination. II

Experimental measurements of ir emission (2<λ<8 μ) from nascent ozone formed by the three−body recombination O+O2+O2→O3+O2 are reported. This represents an extension of earlier work on the fundamental bands (8<λ<15 μ) and includes these results: (a) 4.7 μ data on the (ν1+ν3) combination band, which quantitatively supports our published fundamental band results; (b) 8 μ signals probably due to vibration–rotation transitions of a bound excited triplet state predicted by theoretical calculations; and (c) 6.6 μ emission, which may be due to 3B2→1A1 (forbidden) emission.

Vibrational excitation of ozone formed by recombination

A new facility coupling flash photolysis and time resolved ir detection and uv absorption diagnostics is described. Its application to studying the reaction O+O2+M→ lim (1)u2009O3†+M followed by O3†+M→ lim (2)O3+M with M=O2 or N2 and where O3† denotes vibrationally excited ozone is described. Our results give k1=3×10−34 cm6 sec−1, k2=2×10−14 cm3 sec−1, φ(ν1)+φ(ν3)=1.6, and φ(ν2)=3.7, where φ(νi) is the average number of quanta of energy νi, resulting in mode νi from each recombination (ν1,2,3=1103, 701, 1042 cm−1). This partitioning of the product energy accounts for 50% of the 25 kcal exothermicity of the recombination. These results are peculiar to the model used for interpretation, which is discussed in some detail in the text.

Flash photolysis study of the gas phase recombination of hydroxyl radicals

Rate constants are reported for the reactions OH+OH → H2O+O (where k1 is the rate constant) and OH+OH+N2 → H2O2+N2 (where k5 is the rate constant) measured in a room temperature flash photolysis experiment. Hydroxyl radicals were produced by the photodecomposition of water vapor, and time resolved absorption spectroscopy was utilized to determine the absolute OH concentration. Specific rate constants obtained are k1=2.1±0.2×10−12 cm3/sec and k5=2.5±0.3×10−31 cm6/sec.

Collisional relaxation of electronically excited Pb; 6p2 (3P2) and (3P1)

Time resolved measurements have been made of the room temperature decay of excited electronic states of Pb. The excited atoms were produced by photodecomposition of tetramethyl lead and the concentrations of the excited states were monitored by atomic resonance absorption. Quenching rate constants of the spin orbit states 3P2 and 3P1 were obtained for the collision partners Ar, Xe, H2, D2, N2, and O2. These results are discussed in terms of curve crossings, curve merging, chemical reaction, and E→V energy transfer processes. Comparison is made with the quenching rate constants for these states reported by Husain and Littler.

Electron and heavy particle temperature dependent quenching rate constants of XeF

Two and three body quenching rate constants were determined at 300 and 500u2009°K for a number of quenching gases common to XeF* laser mixtures (Ne, Xe, F2). Among these is the three body quenching of XeF4 by F2 and Xe. In addition, the quenching rate for the reaction XeF*+e− was measured and this process was found to be one of the major quenching channels under typical laser operating conditions.

Temperature dependence of the spin–orbit relaxation of lead, 6p2(3P2) and (3P1)

Rate constants for the collisional deactivation of Pb 6p2(3P2) and (3P1) metastable states are reported over the temperature range 300 to 600u2009°K. Quenching data over this temperature range were obtained for relaxation by Ar, Xe, H2, D2, N2 and by Hg at 373u2009°K. These results were obtained in a temperature controlled, flash photolysis apparatus using tetramethyl lead as a precursor and time resolved atomic resonance absorption techniques for monitoring the 3P2 and 3P1 metastable states of interest.

Pumping iron: A KrF laser pumped atomic iron laser

A technique for producing stimulated emission in an optically pumped atomic iron system at room temperature is described. The required iron density (∼1014 atoms/cm3) for single pass amplified spontaneous emission was produced at room temperature by two techniques: a low pressure (50 torr) discharge of iron pentacarbonyl and neon and by the flash photodecomposition of Fe(CO)5 in an argon buffer. A commercial KrF laser producing output powers near 51 Mw was modified to improve the beam quality, and the beam was focused into the reaction cell. Resonant processes involving the 3d6 4p 4p (5F°) intermediate state of iron and the KrF laser field (λ?248 nm) produced stimulated emission near 300 and 304 nm in agreement with theoretical predictions.

Collisional relaxation of electronically excited copper: 3d9 4s2 (2D5/2)

A flash photolysis experiment whereby optically metastable copper atoms (3d9 4s2 2D5/2) were produced in a high temperature (600u2009°K) reaction cell by the photodecomposition of copper halides (CuCl and CuI) is described. The subsequent decay of these low‐lying electronically excited copper atoms was monitored by time resolved atomic resonance absorption techniques to provide collisional quenching rate constants for relaxation of the 2D5/2 state by He, Ar, Xe, N2, CO, CO2, SF6, and O2.

Temperature dependence of the collisional quenching of electronically excited bismuth atoms: 6p3 (2D03/2) and (2D05/2)

Temperature dependent rate constants are reported for the collisional deactivation of the 6p3 (2D03/2) and 6p3 (2D05/2) states of atomic bismuth by Ar, Xe, N2, H2, D2, CO, O2, CO2, and SF6 at 300, 450, and 550u2009°K. These results are discussed within the context of correlation diagrams constructed using (J,Ω) coupling approximations. Where appropriate, these data are reduced to provide Arrhenius parameters and likely relaxation mechanisms are discussed.