G. P. Glass

Infrared flash kinetic spectroscopy of the ketenyl radical

The high resolution infrared spectrum of the heavy atom antisymmetric stretch of the ketenyl radical (HCCO) has been observed by means of infrared kinetic spectroscopy producing the ketenyl by 193 nm photolysis of ketene with diode laser probing of the transient absorption. Individual rovibrational transitions have been identified near the band origin located at approximately 2023 cm−1. A preliminary kinetic study of the ketenyl radicals reaction with nitric oxide was conducted. A second order rate constant of 3.9(5) × 10−11 cm3 molecule−1 s−1 was obtained for this reaction by following the decay of ketenyl in the presence of excess NO.

Rate of Some Hydroxyl Radical Reactions

The rates of the following reactions of the hydroxyl radical have been measured in a fast flow system using ESR detection: OH+OH→H2O+O, OH+O→H+O2, OH→wall. The rate constants obtained were k1 = 8.4 ± 2.6 × 10−13cm3molecule−1·sec−1, k2 = 4.3 ± 1.3 × 10−11cm3molecule−1·sec−1, and k3 = 124 ± 40 sec−1. The rates of the first two reactions are compared with previous measurements. Earlier investigators have not included the third reaction in their mechanisms. In all experiments, the hydroxyl radicals were generated by means of the titration reaction H + NO2→OH + NO.

The effect of vibrational excitation of H2 and of OH on the rate of the reaction H2+OH→H2O+H

The reaction between the hydroxyl radical and H2 has been studied at room temperature using a discharge flow apparatus equipped for EPR detection of small, free radicals. Vibrationally excited H2 was generated using electric discharge techniques. The rate of the reaction H2+OH→H2O+H was shown to be enhanced by a factor of 155 when H2 was excited into its first vibrational state. Earlier work had shown that the rate of this reaction was increased by less than 50% when OH was excited to either its first or second vibrational state.

The rate of the reaction D+H2(v = 1)→DH+H

The rate constant of the reaction D+H2(v = 1)→DH+H has been measured at 297 K as (9.8±3.0)×10−13 cm3 s−1. The reaction was studied using a discharge flow apparatus equipped for EPR detection of small free radicals. H2(v = 1) was generated using electric discharge techniques. Previous theoretical and experimental studies have been discussed.

Vibrational energy transfer from OH to other gaseous hydrides

Vibrational energy transfer from OH (v=1, 2) to a number of simple hydrides (CH4, NH3, H2O, HCl, H2, D2) has been investigated using a discharge flow apparatus attached to a sensitive EPR spectrometer. Strong similarities between the rate of vibrational energy transfer from OH and the rate of V–V transfer from HCl have been observed. These similarities have been discussed in terms of the mechanism of the energy transfer process.

The relaxation of HCl(ν = 1) and DCl(ν = 1) by O atoms between 196 and 400 K

Abstract The rates of relaxation of HCl(ν = 1) and DCl(ν = 1) by atomic oxygen have been determined between 196 and 400 K using the laser induced vibrational fluorescence method. The values of the rate constants, κ 1,H and κ 1,D , can be matched quite well by Arrhenius expressions: κ 1,H = 6.2 × 10 −12 exp (−1.0 5 kcal mole −1 / RT ) cm 3 molecule −1 s −1 and κ 1,D = 2.9 × 10 −12 exp (−0.5 kcal mole −1 / RT ) cm 3 molecule −1 s −1 . The most likely explanation of the absolute and relative magnitudes of these rate constants appears to be that relaxation occurs as a result of non-adiabatic vibronic transitions during collisions.

Acetylene combustion reactions. Rate constant measurements of HCCO with O2 and C2H2

Abstract The second-order rate constant for the reaction of the ketenyl radical (HCCO) with O 2 was measured at room temperature by using infrared kinetic spectroscopy as 6.5 (6) × 10 −13 cm 3 molecule −1 s −1 . An upper bound for the rate constant for the reaction between HCCO and C 2 H 2 was determined as 1 × 10 −13 cm 3 molecule −1 s −1 . HCCO was produced by 193 nm excimer laser photolysis of ketene and probed with a tunable infrared diode laser operating at 2014 cm −1 .

The photolysis of NO2 at 193 nm

Abstract Infrared kinetic spectroscopy has been used to investigate the photo-dissociation of NO 2 at 193 nm. The O( 1 D)/(O( 1 D)+O( 3 P)) branching ratio was measured as 0.55±0.03 by adding a large excess of H 2 to the system, and comparing the amount of NO 2 removed during the photolysis to the amount of OH formed by the subsequent fast reaction between O( 1 D) and H 2 . The rate constant for the reaction between O( 1 D) and NO 2 was measured as (1.5±0.3)×10 −10 cm −3 s −1 , and the 193 nm absorption cross-section for NO 2 was estimated as (2.9±1.2)×10 −19 cm 2 .

Dominant formation and quenching kinetics of electron beam pumped Xe2Cl

Processes leading to the production and removal of the triatomic excimer Xe2Cl* subsequent to short duration electron beam excitation of Ar/Xe/CCl4 mixtures have been investigated. The radiative lifetime of Xe2Cl* has been measured to be 135 (+70−60) ns. Formation of the excimer has been shown to occur principally via a termolecular reaction involving XeCl*. Rate constants for the formation and collisional quenching of Xe2Cl* by CCl4, Xe, and Ar have been determined.

Rotationally resolved spectrum of the ν1 CH stretch of the propargyl radical (H2CCCH)

Abstract The ν 1 acetylenic CH stretch of the propargyl radical (HCCCH 2 ) near 3322 cm −1 has been observed by infrared laser kinetic spectroscopy at Doppler limited resolution. Propargyl is prepared by flash photolysis of propargyl bromide or propargyl chloride at 193 nm and its transient infrared absorption probed by a cw color center laser. The spectrum consists, as is expected, of only a-type (Δ K =0) transitions, and near the origin appears quite simple resembling that of a diatomic molecule. This means that the A and D K rotational constants in the upper state must differ little from the ground state so that the various K subbands overlap almost exactly. However, at N ⩾14 the spectrum no longer has this regular pattern, probably because of perturbations of the excited state by nearby vibrational levels. Ground and excited state rotational constants were determined by fitting the K =1 lines having N ″