Engineering topics

Pattengill, M. D.

Publications and source records attributed to Pattengill, M. D..

8 records

NASA NTRS1987

Ca + HF - The anatomy of a chemical insertion reaction

A comprehensive first-principles theoretical investigation of the gas phase reaction Ca + HF - CaF + H is reported. Ab initio potential energy calculations are first discussed, along with characteristics of the computed potential energy surface. Next, the fitting of the computed potential energy points to a suitable analytical functional form is described, and maps of the fitted potential surface are displayed. The methodology and results of a classical trajectory calculation utilizing the fitted potential surface are presented. Finally, the significance of the trajectory study results is discussed, and generalizations concerning dynamical aspects of Ca + HF scattering are drawn.

Jaffe, R. L.↗

NASA NTRS1987

Effects of diatomic reagent alignment on the A + BC reaction

A computational study is reported on the A + BC - AB + C bimolecular exchange reaction in which BC is aligned with respect to the approach direction of atom A so that the initial rotational angular momentum vector of BC is either parallel (or equivalently antiparallel) or perpendicular to the initial velocity vector of A. The calculations employ a modification of the extended LEPS potential, which permits straightforward generation of noncollinear minimum energy reaction paths. The calculations clearly demonstrate that diatomic reagent alignment can markedly affect the nature of reaction product early partitioning; they also demonstrate that diatomic reagent alignment affects reactive cross sections.

Pattengill, M. D.↗

NASA NTRS1971

Molecular collisions. XVI.

The comparison indicates that the present version of the GPS method overestimates the rotational excitation and underestimates the de-excitation, while maintaining the total inelasticity at approximately the correct exact classical trajectory value. An approximate ?quantization' of the classical results leads to an estimate of the quantal cross sections corresponding to changes by plus or minus 2, 4, and 6 from an initial rotor quantum state 10. It is found that most of the total inelastic cross section arises from the first-order-allowed transitions.

Pattengill, M. D.↗

NASA NTRS1971

Molecular collisions. XV - Classical limit of the generalized phase shift treatment of rotational excitation- Atom-rigid rotor

Rotationally inelastic molecular collisions in atom rigid rotor scattering, considering infinite order approximation of generalized phase shift treatment

Bernstein, R. B.↗

NASA NTRS1971

Molecular collisions. 16: Comparison of GPS with classical trajectory calculations of rotational inelasticity for the Ar-N2 system

Comparison of generalized phase shift treatment with classical trajectory calculations of rotational inelasticity cross sections of Ar-N2 scattering

Pattengill, M. D.↗

NASA NTRS1971

Molecular collisions. 15 - Classical limit of the generalized phase shift treatment of rotational excitation - Atom-rigid rotor

Generalized phase shift approach to problem of rotationally inelastic molecular collisions

Bernstein, R. B.↗

NASA NTRS1971

Molecular collisions. XIV

Atom rigid rotor problem, applying generalized phase shift rotational excitation treatment in lowest approximation

Bernstein, R. B.↗

NASA NTRS1970

Molecular collisions. 14 - First-order approximation of the generalized phase shift treatment of rotational excitation - Atom-rigid rotor

Applying generalized phase shift approach to rotational excitation problem to atom-rigid rotor case in first order approximation

Bernstein, R. B.↗