Triatomic potential

The minimum of t/ocs corresponds to the equilibrium geometry, and it is very easy to see that it corresponds to l cs = 153.5 pm and J co = 112.8 pm. We might have suspected from our study of normal modes of vibration that the two vibrations would not be independent of each other, so our first guess at a triatomic potential is not very profitable. 

Cooper, I. L., and Levine, R. D. (1989), Construction of Triatomic Potentials from Algebraic Hamiltonians Which Represent Stretching Vibrational Overtones, J. Mol. Struct. 199,201. 

In order that the potential shall be equally suitable for all configurations on the surface we choose as internal coordinates the three bond lengths. We then write the general ABC triatomic potential as... 

Figure 3. Triangular diagram to represent a triatomic potential-energy surface. For any point of the triangle KLM the molecular perimeter is constant, R, + R2 + R3 = constant = /i. The unshaded area of the K L M triangle corresponds to the space physically accessible to the nuclei for that perimeter. Inside the K L M triangle, one has R + R 2 + R = //2, where R (i = 1,2,3) are the Pekeris coordinates.

J.M. Bowman, A. Kuppermann, Semi-numerical approach to construction and fitting of triatomic potential-energy surfaces, Chem. Phys. Lett. 34 (3) (1975) 523-527. 

I. L. Cooper and R. D. Levine, Construction of triatomic potential from algebraic Hamiltonians which represent stretching vibrational overtones,/. Mol. Struct. 191 201 (1989). 

T. Carrington, Triatomic potential surfaces, Faraday Discuss. Chem. Soc. 53 27 (1972). 

To conclude this section, the upper panel of Figure 20.8 displays a non-reactive triatomic potential characteristic of the A + X2 A + X2 system, in which AX does not form a stable bond. This type of potential surface is ideal for studying translational-to-vibrational energy transfer, i.e. theelastic scatteringin... 

It should be stressed that as v increases the equilibrium distance changes from 3.8 A for V = 0 to 4.9 A for V = 5. Thus if we describe the triatomic complex Hg--Ar2 as an atom (Hg) bound to a diatomic molecule (Ar2), the triatomic potential strongly depends on the vibrational state of the diatomic molecule. 

In this appendix the explicit forms of the triatomic potentials and couplings used in the calculations... 

Carrington T (1972) Triatomic potential surfaces. A catalogue of intersections. Discuss Faraday Soc 53 27... 

Contovirs in arbitrary energy units of the potential energy surface for the hypothetical coUnear reaction involving a stable triatomic molecule, ABC. The overall process is A + BC ABC -> AB + C. The horizontal axis is the B-to-C separation distance, and the vertical axis is the A-to-B distance. There is a saddle point between the A + BC trough and the ABC triatomic (potential surface minimvun) and a saddle point between the minimvun and the AB + C trough. 

S. Erkoc, J, N. Murrell, and D. C. Clary, Quantum mechanical calculation of collinear atom-triatom transition probabilities for anharmonic triatom potentials, Chem. Phys. Lett. 72 624 (1980). 

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