Research publications

Permanent URI for this collection

https://hdl.handle.net/10315/2893

Browse

Now showing 1 - 20 of 244

Open Access
The stable carbon kinetic isotope effects of the reactions of isoprene, methacrolein, and methyl vinyl ketone with ozone in the gas phase
(Elsevier, 08-Mar) Iannone, Richard; Koppmann, Ralf; Rudolph, Jochen
The stable-carbon kinetic isotope effects (KIEs) for the gas-phase reactions of isoprene, methacrolein (MACR), and methyl vinyl ketone (MVK) with ozone were studied in a 25 L reaction chamber at (298 ± 2) K and ambient pressure. The time dependence of both the stable-carbon isotope ratios and the concentrations was determined using a gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The volatile organic compounds (VOCs) used in the KIE experiments had natural-abundance isotopic composition thus KIE data obtained from these experiments can be directly applied to atmospheric studies of isoprene chemistry. All 13C/12C KIEs reported herein are as per mille ε values, where ε = (KIE – 1) × 1000‰, and KIE = k12/k13. The following average stable-carbon KIEs were obtained: (8.40 ± 0.11) ‰ (isoprene), (7.67 ± 0.28) ‰ (MACR), and (7.87 ± 0.08) ‰ (MVK). The stable-carbon KIE values of three 1-alkenes, which were used as reference compounds for relative rate experiments, were also determined: (5.48 ± 0.09) ‰ (1-heptene), (4.67 ± 0.17) ‰ (1-octene), and (4.59 ± 0.56) ‰ (1-nonene). The ε values for the reactions of isoprene and 1-heptene with ozone agree with measurements in a previous study, but the values presented here have a substantially improved accuracy. The ε values for 1-octene and 1-nonene reactions with ozone have not been measured before and closely follow the 1/NC dependence (where NC represents the number of carbon atoms in the alkene) observed in previous studies. MACR and MVK had ε values that were somewhat below the expected range of values predicted by the 1/NC dependence found for alkenes.
Open Access
12C/13C kinetic isotope effects of the gas-phase reactions of isoprene, methacrolein, and methyl vinyl ketone with OH radicals
(Elsevier, 09-Mar) Iannone, Richard; Koppmann, Ralf; Rudolph, Jochen
The stable-carbon kinetic isotope effects (KIEs) for the gas-phase reactions of isoprene, methacrolein (MACR), and methyl vinyl ketone (MVK) with OH radicals were studied in a 25 L reaction chamber at (298 ± 2) K and ambient pressure. The time dependence of both the stable-carbon isotope ratios and the concentrations was determined using a gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The volatile organic compounds (VOCs) used in the KIE experiments had natural-abundance isotopic composition thus KIE data obtained from these experiments can be directly applied to atmospheric studies of isoprene chemistry. All 13C/12C KIE values are reported as ε values, where ε = (KIE – 1) × 1000‰, and KIE = k12/k13. The following average stable-carbon KIEs were obtained: (6.56±0.12)‰ (isoprene), (6.47±0.27)‰ (MACR), and (7.58±0.47)‰ (MVK). The measured KIEs all agree within uncertainty to an inverse molecular mass (MM) dependence of OHε(‰) = (487±18)MM–1,which was derived from two previous studies [J. Geophys. Res. 2000, 105, 29329–29346; J. Phys. Chem. A 2004, 108, 11537–11544]. Upon adding the isoprene, MACR, and MVK OHε values from this study, the inverse MM dependence changes only marginally to OHε(‰) = (485±14)MM–1. The addition of these isoprene OHε values to a recently measured set of O3ε values in an analogous study [Atmos. Environ. 2008, 42, 8728–8737] allows for estimates of the average change in the 12C/13C ratio due to processing in the troposphere.
Open Access
Real time measurement of PAN using SIFT-MS
(Wiley-Blackwell, 09-Nov) Hastie, D.R.; McEwan, M.J.; Maclagan, G.A.R.; Milligan, D.; Gray, J.; Langford, V.S.
The on-line detection of gaseous peroxyacetyl nitrate (PAN) using SIFT-MS has been investigated using a synthetic sample of PAN in air at a humidity of ~30%. Using the H3O+ reagent ion, signals due to PAN at m/z 122, 77 and 95 have been identified. These are the protonated PAN, protonated peractetic acid and its water cluster respectively. .These products and their energetics have been probed through quantum mechanical calculations. The H3O+ rate coefficient has been estimated to be 4.5x10-9 cm3 s-1 leading to a PAN sensitivity of 138 cps/ppbv. This gives a limit of detection of 20 pptv in 10 s using the m/z 122 product ion.
Open Access
Search for Actinides by Secondary Reactions in Tungsten and Gold
(1974) Lieser, H.; Bachmann, K.; Ross, E.; Molzahn, D.; Malek, Z.; Rudolph, J.
Abstract··- Tungsten and gold have been irradiated with 24 GeV and 10·8 GeV protons. resp.. and the possible production of actinide nuclides by secondary reactions has been investigated. The actinide fractions were chemically separated and IX-spectra taken. No IX-peaks which could definitely be attributed to actinide nuclides could be found. By taking different formation mechanisms into consideration. upper limits fM the cross-sections were calculated and compared with the values expected.
Open Access
Excited State Formation in the H + O2 System
(Elsevier, 1975) Giachardi, D.J.; Harris, G.W.; Wayne, R.P.
Open Access
The Reactions of Ozone with Methyl and Ethyl Nitrites
(Wiley-Blackwell, 1976) Hastie, D.R.; Freeman, C.G.; McEwan, M.J.; Schiff, H.I.
The reactions of O3 with CH3ONO and C2H5ONO were studied using infrared absorption spectroscopy in a static reactor at temperatures between 298 and 352K
Open Access
Pressure Broadening of the Lowest Rotational Transistion of OH Studied by LMR
(Elsevier, 1979) Burrows, J.P.; Cliff, D.I.; Harris, G.W.; Thrush, B.A.; Wilkinson, J.P.T.
Open Access
Determination of Adsorption enthalpies and entropies of Inorganic Halides by Temperature Programmed Gas Chromatography
(1979) Bachmann, K.; Rudolph, J.
The possibilities of using temperature-programmed gas-solid chromatography· for the determination ofadsorption enthalpies and entropies of inorganic chlorides are investigated. This method is suitable, if data oflimited accuracy are acceptable, whereas for more precise data isothermal gas chromatography is recommended. The advantage of temperature-programmed experiments is that simultaneous investigations can be made ofcompounds with very different volatilities. The results of these investigations support the picture of "surface complexes" bet\veen the adsorbed molecules (metal halides or oxyhalides, e.g., ReCls _ SnCl.s, PoCl.s. etc.) and the adsorbent (alkali metal halides. SiO.!).
Open Access
Temperature Dependence of the Reaction OH + SO2 + M = HSO3 + M for M = AR and SF6
(Elsevier, 1980) Harris, G.W.; Atkinson, R.; Pitts Jr., J.N.
Open Access
The Use of Isothermal Gas Chromatography for the Determination of Adsorptionenthalpies and entropies of Inorganic Halides at High Temperatures
(1980) Rudolph, J.; Bachmann, K.
Gas chromatography was used to determine the adsorption enthalpies and entropies of inorganic chlorides on sslid non-porous adsorhents (silica, alkali metal chlorides, graphite, etc.) at high temperatures (65th1100°K). The results demonstrate that gas chromatography is also a useful method for investigations in the field of inorganic chemistry. The adsorption enthalpies and entropies (or rather, chemisorption enthdpies and entropies) indicate that the adsorption (or chemisorption proCess>i nvolves complex formation between the adsorbed molecules and the adsorbent (coordinative by bonded surface complex).
Open Access
Finite-time thermodynamics: engine performance Improved by optimized piston motion
(National Academy of Science, 1981) Mozurkewich, M.; Berry, R.S.
The methods of finite-time thermodynamics are used to find the optimal time path of an Otto cycle with friction and heat leakage. Optimality is defined by maximization of the work per cycle; the system is constrained to operate at a fixed frequency, so the maximum power is obtained. The result is an improvement of about 10% in the effectiveness (second-law efficiency) of a conventional near-sinusoidal engine.
Open Access
Vertical Profiles of Ethane and Propane in the Stratosphere
(AGU, 1981) Rudolph, J.; Ehhalt, D.H.; Tonnissen, A.
Stratospheric measurements of the C2H6 mixing ratio up to 30 km and of the C3H8 mixing ratio up to 18 km altitude are reported. The observed vertical gradient of C2H6 is much weaker than that calculated from a one-dimensional steady state model, indicating lower concentrations of atomic chlorine in the lower stratosphere than those predicted by models. From the measured C2H6 profile a tentative estimate for the Cl concentration is derived.
Open Access
Stratospheric Odd Nitrogen: NO Measurements at 51°N in Summer
(AGU, 1981) Ridley, B.A.; Hastie, D.R.
The altitude distribution of nitric oxide was measured during three balloon flights in August 1976 and 1978. Median values of the volume mixing ratio at 18, 24, 30, and 34 km were 0.4, 1.4, 6.5, and 13 ppb, respectively. The data are discussed in relation to an average profile of nitrogen dioxide measured for this season and latitude and in relation to current one-dimensional models of the stratosphere.
Open Access
Rate Constants for the Reactions of OH Radicals with CH3CN, C2H5CN and CH2=CH.CN in the Temperature Range 298 to 424K
(Elsevier, 1981) Harris, G.W.; Kleindienst, T.E.; Pitts Jr., J.N.
Open Access
Maximum work from a finite reservoir by sequential Carnot cycles
(American Association of Physics Teachers, 1981) Ondrechen, M.J.; Anderson, B.; Mozurkewich, M.; Berry, R.S.
The production of work from a heat source with finite heat capacity is discussed. We examine the conversion of heat from such a source first by a single Carnot engine and then by a sequence of Carnot engines. The optimum values of the operating temperatures of these engines are calculated. The work production and efficiency of a sequence with an arbitrary number of engines is derived, and it is shown that the maximum available work can be extracted only when the number of cycles in the sequence becomes infinite. The results illustrate the importance of recovery or bottoming processes in the optimization of work-producing systems. In addition, the present model illuminates one practical limitation of the Carnot cycle: The Carnot efficiency is only obtainable from a heat source with infinite heat capacity. However, another cycle, somewhat reminiscent of the Otto and Brayton cycles, is derived which will provide the maximum efficiency for a heat source with a finite heat capacity.
Open Access
Measurements of the Relative Rate Constants for the Quenching of O(1D) Atoms by N2O and N2 and the Branching Ratio of the N2O Reaction at 23°C and -96°C
(Elsevier, 1981) Lam, Lisa; Hastie, D.R.; Ridley, B.A.; Schiff, H.I.
Open Access
DETERMINATION OF C2-C5 HYDROCARBONS IN THE ATMOSPHERE AT LOW PARTS PER 109 TO HIGH PARTS PER 1012 LEVELS
(1981) Khedim, A; Ehhalt, D.H; Rudolph, J.; Jebsen, C
By far the most abundant hydrocarbon in unpolluted air is methane (mixing ratio cu. 1.6 ppm). The mixing ratios of other hydrocarbons are typically in the low parts per lo9 (ppb) and parts per 10” (ppt) ranges. Although methane is several orders of magnitude more abundant in clean air, it is conceivable that other hydrocarbons are still of considerable importance to clean air photochemistry, because their reaction with hydroxyl radicals proceeds much faster than that of methane. Owing to this high reactivity of many of the light non-methane hydrocarbons (NMHC), mixing ratios of NMHC as low as a few ppb or several ppt can have a considerable influence on the photochemistry of unpolluted air. For this reason a gas chromatographic method has been developed that permits the determination of several C2-C, hydrocarbons with detection limits of a few ppt from grab samples of 0.5-Z dm3 (STP). The samples are collected in evacuated 2-1 stainless-steel containers with metal bellows-sealed stainless-steel valves. These sample collection and storage cans are specially pre-treated and cleaned to avoid changes in sample composition during transport of the samples to the laboratory. In the laboratory the samples are analysed by enrichment of the hydrocarbons on a packed pre-column at sub-ambient temperatures (L’LI. - 35°C) and subsequent separation on a 7 m x 0.8 mm I.D. packed column (Spherosil XOB 075). A flame-ionization detector is used. This method allowed survey measurements on a global scale of C,-C, hydrocarbons. which gave an estimate of the contributions of light hydrocarbons to atmospheric photochemical reactions.
Open Access
Measurements of C2-C5 Hydrocarbons Over the North Atlantic
(1981) Rudolph, J.; Ehhalt, D.H.
Latitudinal distributions of ethane, propane, propene, and acetylene in air over the Atlantic from 48°N to 4°S are reported. In addition, measurements of saturated and unsaturated hydrocarbons (C2-C5) at low latitudes and from 55°N to 80°N are presented. The mixing ratios of ethane, propane, and acetylene were found to vary systematically between a few tenths of a ppb and a few ppb. The alkene and higher alkane (C4 and C5) mixing ratios were found to be in the ppt range. The data are discussed with respect to the source distributions and atmospheric lifetimes of the different hydrocarbons.
Open Access
Optimal paths for thermodynamic system: the ideal Otto cycle
(American Institute of Physics, 1982) Mozurkewich, M.; Berry, R.S.
We apply the method of optimal control theory to determine the optimal piston trajectory for successively less idealized models of the Otto cycle. The optimal path has significantly smaller losses from friction and heat leaks than the path with conventional piston motion and the same loss parameters. The resulting increases in efficiency are of the order of 10%.
Open Access
Measurements of Nitric Oxide During a Stratospheric Warming
(AGU, 1982) Knight, W.; Hastie, D.R.; Ridley, B.A.
The altitude distribution of NO was measured between 12 and 33 km near 54°N during the stratospheric warming of February, 1979. The NO mixing ratios were considerably smaller compared to summer conditions, especially below 23 km. The measurements are used to estimate the distribution of NO2 for comparison with ground‐based column measurements and to show that during the warming NOx is at least a factor of two lower than is observed in summer at this latitude. This reduction in NOx is shown to be consistent with a larger fraction of odd‐nitrogen existing as N2O5.