Engineering topics

Calvert, J. G.

Publications and source records attributed to Calvert, J. G..

4 records

NASA NTRS1991

An upper limit for the rate coefficient of the reaction of NH2 radicals with O2 using FTIR product analysis

Fourier transform infrared spectrometry has been used to study the products of the photooxidation of ammonia in the presence of oxygen at 296 K. The data have been used to derive an upper limit of 6 x 10 exp -21/cu cm molecule s for the reaction of NH2 radicals with O2 to produce NO(x) at 296 K. This upper limit, which is three orders of magnitude lower than previous estimates based on the kinetics of NH2 loss, rules out the importance of this reaction in the atmosphere and suggests that NH2 will be oxidized by O3 or NO2. The effect on the NO(x) and N2O budgets depends critically on the products of the NH2 + O3 reaction. Simulations of the experimental product yields also allow an evaluation of possible product channels for the reaction of NH2 with HO2.

Tyndall, G. S.↗

NASA NTRS1988

The equilibrium constant for N2O5 = NO2 + NO3 - Absolute determination by direct measurement from 243 to 397 K

Direct determinations of the equilibrium constant for the reaction N2O5 = NO2 + NO3 were carried out by measuring NO2, NO3, and N2O5 using long-path visible and infrared absorption spectroscopy as a function of temperature from 243 to 397 K. The first-order decay rate constant of N2O5 was experimentally measured as a function of temperature. These results are in turn used to derive a value for the rate coefficient for the NO-forming channel in the reaction of NO3 with NO2. The implications of the results for atmospheric chemistry, the thermodynamics of NO3, and for laboratory kinetics studies are discussed.

Cantrell, C. A.↗

NASA NTRS1987

Temperature variable long path cell for absorption measurements

The design and construction of a long path cell for absorption measurements at temperatures ranging from 215-470 K and at pressures from vacuum to 10 atm are described. The cell consists of three concentric stainless-steel tubes; the innermost tube is 6.5-in. in internal diameter, has a volume of about 47 l, and contains White-type optics, six thermocouples, and a gas input tube; and the outermost tube provides a vacuum Dewar around the inner assembly. The optical design and temperature control system for the long path temperature variable cell are examined. The long path cell is applicable for analyzing temperature and pressure dependence of spectra and reaction rates of gases, and the cell has flow and photolysis capabilities for studying transient species and photochemically initiated reactions. A diagram of the cell is provided.

Shetter, R. E.↗

NASA NTRS1980

Band analysis by spectral curve fitting

A method of estimating the values of the parameters in the models describing the positions, widths, and intensities of the lines in rotation-vibration bands of gases, without the need for line by line analysis, is described. To illustrate the technique, portions of the 1-0 bands of HCl and CO have been analyzed. The values of up to 27 parameters, their standard deviations, and the correlations between the parameters required to describe the spectra have been obtained.

Lin, C. L.↗