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112 results on '"Mackay, G. I."'

4. A tunable diode laser system for aircraft measurements of trace gases

Author

Schiff, H. I, Karecki, D. R, Harris, G. W, Mackay, G. I, and Hastie, D. R

Subjects
Lasers And Masers
Abstract

The advantages of tunable-diode-laser absorption spectrometry (TDLAS) for measuring trace atmospheric gases are universality, positive identification, good sensitivity, and rapid response time. A TDLAS system is described which is capable of making measurements aboard an aircraft. The instrument was employed during the Chemical Instrumentation Test and Evaluation (CITE) 2 program to measure NO2 on 11 flights and HNO3 on five flights. Detection limits were determined to be 25 parts per trillion by volume (pptv) for NO2 and 75 pptv for HNO3 with response times of 3 min. This was sufficient to permit measurements of NO2 in the free troposphere and HNO3 in the continental boundary layer a significant fraction of the time.

Published
1990

20. Ratios of peroxyacetyl nitrate to active nitrogen observed during aircraft flights over the eastern Pacific Oceans and continental United States

Author

Ridley, B. A., primary, Shetter, J. D., additional, Gandrud, B. W., additional, Salas, L. J., additional, Singh, H. B., additional, Carroll, M. A., additional, Hübler, G., additional, Albritton, D. L., additional, Hastie, D. R., additional, Schiff, H. I., additional, Mackay, G. I., additional, Karechi, D. R., additional, Davis, D. D., additional, Bradshaw, J. D., additional, Rodgers, M. O., additional, Sandholm, S. T., additional, Torres, A. L., additional, Condon, E. P., additional, Gregory, G. L., additional, and Beck, S. M., additional

Published
1990
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21. An intercomparison of airborne nitric acid measurements

Author

Gregory, G. L., primary, Hoell, J. M., additional, Huebert, B. J., additional, Van Bramer, S. E., additional, LeBel, P. J., additional, Vay, S. A., additional, Marinaro, R. M., additional, Schiff, H. I., additional, Hastie, D. R., additional, Mackay, G. I., additional, and Karecki, D. R., additional

Published
1990
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22. An intercomparison of airborne nitrogen dioxide instruments

Author

Gregory, G. L., primary, Hoell, J. M., additional, Carroll, M. A., additional, Ridley, B. A., additional, Davis, D. D., additional, Bradshaw, J., additional, Rodgers, M. O., additional, Sandholm, S. T., additional, Schiff, H. I., additional, Hastie, D. R., additional, Karecki, D. R., additional, Mackay, G. I., additional, Harris, G. W., additional, Torres, A. L., additional, and Fried, A., additional

Published
1990
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23. Aircraft measurements of NOx over the eastern Pacific and continental United States and implications for ozone production

Author

Carroll, M. A., primary, Hastie, D. R., additional, Ridley, B. A., additional, Rodgers, M. O., additional, Torres, A. L., additional, Davis, D. D., additional, Bradshaw, J. D., additional, Sandholm, S. T., additional, Schiff, H. I., additional, Karecki, D. R., additional, Harris, G. W., additional, Mackay, G. I., additional, Gregory, G. L., additional, Condon, E. P., additional, Trainer, M., additional, Hubler, G., additional, Montzka, D. D., additional, Madronich, S., additional, Albritton, D. L., additional, Singh, H. B., additional, Beck, S. M., additional, Shipham, M. C., additional, and Bachmeier, A. S., additional

Published
1990
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24. Intercomparison of NO2measurement techniques

Author

Fehsenfeld, F. C., primary, Drummond, J. W., additional, Roychowdhury, U. K., additional, Galvin, P. J., additional, Williams, E. J., additional, Buhr, M. P., additional, Parrish, D. D., additional, Hübler, G., additional, Langford, A. O., additional, Calvert, J. G., additional, Ridley, B. A., additional, Grahek, F., additional, Heikes, B. G., additional, Kok, G. L., additional, Shetter, J. D., additional, Walega, J. G., additional, Elsworth, C. M., additional, Norton, R. B., additional, Fahey, D. W., additional, Murphy, P. C., additional, Hovermale, C., additional, Mohnen, V. A., additional, Demerjian, K. L., additional, Mackay, G. I., additional, and Schiff, H. I., additional

Published
1990
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37. Gas-phase reactions of anions with halogenated methanes at 297 ± 2 K

Author

Tanaka, K., Mackay, G. I., Payzant, J. D., and Bohme, D. K.

Abstract

The rate constants for a number of exothermic displacement (SN2) reactions of the type X− + CH3Y → Y− + CH3X where X− = H−, O−, C−, F−, S−, Cl−, OH−, C2−, CN−, SH−, S2−, C2H−, NH2−, NO2−, CHF−, CH2Cl−, CH2Br−, CH3O−, CH3S−, and CH3NH−and Y = F, Cl, and Br, have been measured in the gas phase at 297 ± 2 K using the flowing after-glow technique. These gas-phase measurements provided an opportunity to determine the intrinsic nucleophilic reactivity of 'nude' anions and hence to assess the role of solvation in the kinetics of SN2 reactions proceeding in solution. Comparisons of the experimental rate constants with rate constants calculated using classical theories of capture indicate that several displacement reactions may possess large intrinsicenergies of activation, . Correlations were found between apparent activation energies and the heats of reaction. These correlations provided a convenient classification of the various anion nucleophiles. Displacement was observed to compete with proton transfer in reactions involving nucleophiles of high intrinsic basicity and with hydrogen atom transfer and H2+transfer in the reactions of the O−radical anion.

Published
1976
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39. Equilibrium OH− + C2H2 ⇄; C2H− + H2O and the determination of Δ H°f,298 (C2H−)

Author

Bohme, D. K., Mackay, G. I., Schiff, H. I., and Hemsworth, R. S.

Abstract

The kinetics of the proton transfer reaction OH− + C2H2 ⇄; C2H− + H2O have been investigated at 296°K with the flowing afterglow technique. The rate constants were determined to be kforward = (2.2±0.4) × 10−9 cm3 molecule−1 sec−1 and kreverse = (9.3±3.7) × 10−15 cm3 molecule−1 sec−1. The ratio of rate constants, kf/kr = (2.4±1.0) × 105, was found to be in agreement with the equilibrium constant, K = (2.5±1.0) × 105, determined from equilibrium concentrations. The best estimate of the true value of K corresponds to a standard free energy change, ΔG°296, of −7.3±0.2 kcal mole−1. An estimate of the standard entropy change, ΔS°298, of +3.6 cal deg−1 mole−1 leads to a standard enthalpy change, ΔH°298, of −6.2±0.5 kcal mole−1 and a value for ΔH°f,298 (C2H−) = 71.5±1.1 kcal mole−1. O− was observed to react rapidly with C2H2, k=(2.0±0.4) × 10−9 cm3 molecule−1 sec−1, principally by associative detachment and proton transfer. The reaction of O2− with C2H2 was observed to be slow, k ≤ 1 × 10−12 cm2 molecule−1 sec−1.

Published
1974

40. Measurements of H2O2 and HCHO by Tunable Diode Laser Absorption Spectroscopy During the 1986 Carbonaceous Species Methods Comparison Study in Glendora, California

Author

Mackay, G. I., Mayne, L. K., and Schiff, H. I.

Abstract

An improved, high sensitivity, tunable diode laser spectrometer system designed for tropospheric air measurements (TAMS-150) was employed during the 1986 Carbonaceous Species Methods Comparison Study at Glendora, CA. The TAMS-150 made simultaneous measurements of H2O2 and HCHO with a time response of 3 minutes per data point. The minimum detection limits were respectively 0.1 ppbv and 0.15 ppbv for HCHO and H2O2 and the estimated accuracies were ± 20% for both species. During the first 5 days of the study H2O2 showed little diurnal variation ranging between 0.25 and 0.5 ppbv with maximum values occurring at 15:30 PDT. During the final 4 days H2O2 showed stronger diurnal behavior with mixing ratios ranging from below the detection limits during some nighttime periods to as high as 1.8 ppbv during midday maxima which occurred about 15:30 PDT. HCHO showed strong diurnal behavior throughout the study with rapid changes in concentration in the early morning and evening. Mixing ratios were typically in the range 5-20 ppbv with maxima at about 10:00 and 14:00 PDT.

Published
1990
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41. Collisional Deactivation Rates of N2+(B2Σu+)

Author

Mackay, G. I. and March, R. E.

Abstract

Electron beam excitation of nitrogen was utilized to produce ions in the zeroth and first vibrational levels of the B2Σu+state. The rate constants for the collisional deactivation of electronically excited N2+, for each of N2and NO, were determined individually for the v′ = 0 and v′ = 1 vibrational levels of the N2+(B2Σu+) state. Charge transfer is the most probable mode of deactivation.

Published
1971
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