Soot particle measurements in diffusion flames

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=912608

Laser-induced incandescence measurements of soot production in steady and flickering methane, propane, and ethylene diffusion flames

A four-dimensional intermolecular potential energy surface for the carbon dioxide dimer has been computed using the many-body symmetry-adapted perturbation theory (SAPT) and a large 5s3p2d1f basis set including bond functions. The SAPT level applied is approximately equivalent to the supermolecular many-body perturbation theory at the second-order level. An accurate fit to the computed data has been obtained in a form of an angular expansion incorporating the asymptotic coefficients computed ab initio at the level consistent with the applied SAPT theory. A simpler site-site fit has also been developed to facilitate the use of the potential in molecular dynamics and Monte Carlo simulations. The quality of the new potential has been tested by computing the values of the second virial coefficient which agree very well with the experimental data over a wide range of temperatures. Our potential energy surface turns out to be substantially deeper than previous ab initio potentials. The minimum of −484 cm−1 has ...

Intermolecular potential of carbon dioxide dimer from symmetry-adapted perturbation theory

The development is described of a basis set of moderate size optimized for the computation of the dipole polarizability of reasonably large molecules consisting of hydrogen and p-block elements up to iodine. The mean polarizability, polarizability anisotropy and dipole moment for hydrides of the first four rows of the periodic table, obtained at both the SCF and MP2 levels, are compared with those obtained using the previously developed 6–31 G(+ sd + sp) basis set, as well as larger basis sets, and with experiment. For the series of diatomic halogens, X2, and the halomethanes, CH3X (X = F, C1, Br, I), electric properties are obtained in excellent agreement with those resulting from use of larger basis sets, and also with experiment.

Accurate prediction of static dipole polarizabilities with moderately sized basis sets

The electric quadrupole moments of a number of molecules have been determined from measurement of the birefringence induced in a gas by an electric field gradient. The values obtained are: carbon dioxide (− 14·27 ± 0·61)x 10−40 C m2, carbon monoxide (− 9·47 ± 0·15)x 10−40 C m2, nitrogen (− 4·65±0·08)x 10−40 C m2 and boron trifluoride (12·6±0·7)x 10−40 C m2. In the calculation of the moments for carbon monoxide and boron trifluoride the small hyperpolarizability contribution was neglected in the absence of known values. By means of the Jones calculus a detailed analysis was made of the effects of strain birefringence in the cell windows and imperfect orientation of polarizing components in the light path. This analysis led to a measurement procedure which yielded results significantly different from previously reported ones obtained with essentially the same apparatus. The probable error in the earlier procedure is identified.

Measurement of the electric quadrupole moments of CO2, CO, N2, Cl2 and BF3

The depolarization ratio for Rayleigh scattering by 39 molecular species are reported for λ= 488.0, 514.5 and 632.8 nm. The literature has been critically surveyed for refractivities which are used in conjunction with the observed depolarization ratios to yield the anisotropy of the molecular polarizability of the molecules. Results are given for CO2, OCS, CS2, C2H6, C3H8, isobutane, cyclopropane, C2H4, allene, C2H2, methylacetylene, dimethylacetylene, spiropentane, cyclohexane, C6H6, C6H5F, 1,3,5-C6H3F3, C6F6, CH3CN, (CH3)2CO, CH3F, CH2F2, CHF3, CH3Cl, CH2Cl2, CHCl3, CF2Cl2, CH3Br, CH3I, t-butylchloride, t-butylbromide, ethylene oxide, (CH3)2O, (CH3)2S, H2S, SO2, N2, N2O and CO.

Allan H. White

Papers

Rayleigh scattering depolarization ratio and molecular polarizability anisotropy for gases