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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Theoretical study of the dissociation energy and the red and violet band systems of CN

The dissociation energy D0 is determined here for the CN ground-state and radiative lifetimes for the A 2Pi and B 2Sigma(+) states. D0 is found to be 7.65 + or - 0.06 eV, corresponding to Delta Hf (CN) = 105.3 + or - 1.5 kcal/mole. These results are compared with current experimental estimates and with previous theoretical calculations.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1987

Theoretical study of the dissociation energy and the red and violet band systems of CN

The dissociation energy (D sub O) of CN is determined to be 7.65 + or - 0.06 eV. This corresponds to delta H sub f (CN) = 105.3 + or - 1.5 kcal/mole, in excellent agreement with Engleman and Rouse (1975), but considerably larger than the recent value deduced from shock-tube studies by Colket (1984). The result is obtained not only from extensive ab initio MRCI calculations using a very large Gaussian basis set, but also from extrapolation of the directly computed value by comparison of computed and experimental results fo NO, C2, and N2. As an additional calibration of the methods, the D sub O value for CN was computed from the corresponding value for CN(-) using the experimental electron affinity data. The lifetime of the nu prime = 0 level of the violet (B 2 sigma + yields X 2 sigma +) system was computed to be 62.4 ns, in good agreement with both experiment and previous calculations. Lifetimes for the red (A 2 pi yields X 2 sigma +) system decrease with increasing nu prime, which is consistent both with the recent experiment and calculations. While the computed lifetimes are significantly longer that those obtained from the experiment, they are shorter than those deduced from an analysis of the solar spectrum. However the D sub O and f (sub OO) are consistent with Lambert's model for the solar spectrum.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1992

Theoretical study of the bond dissociation energies of propyne (C3H4)

The C-C and C-H bond dissociation energies (BDEs) of propyne have been computed using the modified coupled-pair functional method. Due to hyperconjugation, the C-C and methyl C-H single bonds are stronger and weaker, respectively than those in ethane. The acetylenic C-H and C triple bond C BDEs are larger and smaller, respectively, than in acetylene, also as a result of the hyperconjugation. Our best estimate of 92.5 +/- 2 kcal/mol for the methyl C-H BDE in propyne is slightly larger than the experimental value. For the acetylenic C-H BDE in propyne we predict 135.9 +/- 2 kcal/mol.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1990

Theoretical study of the C-H bond dissociation energy of C2H

A theoretical study of the convergence of the C-H bond dissociation energy D(0) in C2H with respect to both the one- and n-particle spaces is presented. The calculated C-H bond energies of C2H2 and C2H4, which are in excellent agreement with experiment, are used for calibration. The best estimate for D(0) of 112.4 + or - 2.0 kcal/mol is slightly below the recent experimental value of 116.3 + or - 2.6 kcal/mol, but substantially above a previous theoretical estimate of 102 kcal/mol. The remaining discrepancy with experiment may reflect primarily the uncertainty in the experimental D(0) value of C2 required in the analysis.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1973

A shock-tube determination of the CN ground state dissociation energy and electronic transition moments for the CN violet and red band systems

The CN ground state dissociation energy and the sum of squares of the electronic transition moments of the CN violet bands have been simultaneously determined from spectral emission measurements behind incident shock waves. The unshocked test gases were composed of various CO2-CO-N2-Ar mixtures, and the temperatures behind the incident shocks ranged from 3500 to 8000 K. The variation of the electronic transition moment with internuclear separation was found to be small for both the CN violet and red band systems.

Arnold, J. O.↗