ENERGY TRANSFER ATTENDING COLLISIONS OF ATOMS WITH DIATOMIC MOLECULES

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1963

OSTI ID:4007732

Jameson, A K

A study of vibrational energy transfer attending collisions of ntoms with homonuclear diatomic molecules was carried out. A model obeying classical mechanics was assumed and calculations were carried out for various initial conditions. The potertial energy for the three body system was taken to be the sum of three two-body potentials, namely: two Lennard-Jones potentials, representing the atom-molecule interaction, and one Morse potential, representing the diatomic molecule. Collisions studied were limited to the collinear variety and to perpendicular interactions in which the atom approached the center of mass of the molecule; in each instance the molecule possessed no rotational energy. The variables and parame ters studied were translational and vibrational energies, vibrational phase angles, atomic and molecular masses, and molecular force constants. The resulting initial value problems were solved by numerical integration of the differential equations of motion on a digital computer, the Illiac. Comparison of the results, for no initial vibrational energy, with the analytical calculations of Rapp indicated agreement as to order of magnitude even though Rapp used an exponential repulsive potertial. The energy transfer of collisions involving non-zero initial vibrntional energy was analyzed in terms of a Fourier series in the vibrational phase angie. An arbitrary change was made in the phase angle to render the sum of the coefficients of the cosine terms equal to zero. For collinear hard sphere collisions the analytic calculation of energy transfer was expanded in a Fourier series and compared with the numerical calculations involving the more realistic Lennard-Jones irteraction. Although the hard sphere analysis proved invalid, some Fourier coefficients had the same dependence on translational and vibrational energies. It was also found thnt the diatomic molecule was well represented by a harmonic potertial function for initial vibrational energies below about one half the dissociation energy. The most interesting result was the comparison of the relative values of the energy transferred in collinear and perpendicular collisions. For heavy molecules and light atoms, collinear collisions are more important than perpendicular ones for large energy transfer. For light molecules and heavy atoms, on the other hand, perpendicular collisions are more important than the collinear variety for large energy transfer. Indeed, in some cases the relative values of the first Fourier coefficients of the sine series differed by an order of magnitude, with that for perpendicular being the higher of the two. (Dissertation Abstr., 24: No. 9, March 1964).

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-18-020776
• OSTI ID: 4007732
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ATOMIC MODELS
ATOMS
BINDING ENERGY
COLLISIONS
COMPUTERS
DIFFERENTIAL EQUATIONS
DIGITAL SYSTEMS
DISSOCIATION ENERGY
ELECTRIC POTENTIAL
ENERGY
FOURIER ANALYSIS
ILLIAC
INTERACTIONS
LENNARD-JONES POTENTIAL
MANY BODY PROBLEM
MASS
MATHEMATICS
MECHANICS
MOLECULES
MORSE POTENTIAL
NUMERICALS
OSCILLATIONS
PHYSICS
ROTATION
SPHERES
THERMODYNAMICS
VIBRATIONS