A Spherically Symmetric Potential for Ar*(3P2 ̣0)+O2 from Velocity Dependent Total Cross Sections

Document Type



Master of Science (MS)



First Advisor's Name

Kenneth A. Hardy

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Yesim Darici

Third Advisor's Name

Jeffrey A. Joens

Fourth Advisor's Name

John W. Sheldon

Date of Defense



Velocity dependent total cross sections σ(g) were measured for Ar* (3P2,0)-O2 in the range covering 600-3000 ms-1 using a single beam technique. The measured cross sections σ(g) were determined from the attenuation of the statistically mixed (the 3P2 dominates the 3P0 state by a ratio of 5:1) Ar* beam due its interaction with O2, which was contained in a scattering cell. The absolute value and velocity dependence of σ(g) give information on the long range forces and well area of the potential. The parameters Σ and Rm (Σ is the well depth and Rm is the well position) were derived by a semiclassical inversion technique. These parameters were Σ = 9.73 x 10-5 au. and Rm = 8.60 au.

Using the parameters obtained from the semiclassical inversion technique as input, the measured cross sections were compared to those obtained from a numerical integration of the Schrodinger equation using an assumed potential of the form:

V(r) = (Σ[(f+5)/(n-5) (Rm/R)n - [n(1-f)+6f]/(n-5) (Rm/R)5
- f(Rm/R)6]

The 1/R5 dependence in the potential is a measure of a quadrupole-quadrupole interaction. This dependence is believed to be present in the Ar*-O2 system, as both Ar* and O2 have quadrupole moments. The resulting potential parameters were (Σ = 9.24 10-5 au., n = 10, Rm = 9.00 au., and f = 1.27.

The ratio of the C5 terms (C5 = [n(1-f)+6f)/(n-5)]RM5 For the Ar*-O2 and Ar*-N2 systems, which should be proportional to the ratio of their quadrupole moments for O2 and N2, was computed. This ratio was found to be:

C5(N2)/C5(O2) = 1.25

This ratio is of the same order of magnitude as the ratio of the quadrupole moments for O2 and N2.



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