Classification of Negative-Ion Morse Potentials

The Morse potentials for the neutral and HIMPEC as referenced to zero energy at infinite separation are given by 

The negative-ion properties have not been measured directly. Therefore, it is necessary to combine data from different sources to obtain the dimensionless parameters to define the curves. Three data points on the curve will define a negative-ion curve. The Herschbach metrics EDEA, Ea, and VEa give kA and kR from equations 7.3 and 7.6 since the De(X2(—)) are directly related to the Ea and EDEA. This only gives two constants since the EDEA is a displacement of the negative-ion curve from the neutral, and a third point is required. The v,.(X2( )) or re(X2(—)) gives kR from equation 7.4 or 7.5 to define the anion Morse potentials. 

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Figure 2.4 Classification of negative-ion Morse potential energy curves originally presented by Herschbach in 1966. The curves are calculated from actual data. The empty spaces are impossible combinations. These classifications have been modified so that they are symmetrical and all combinations are possible [34, 36].

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