Total ionisation asymmetry

The measurement of the total ionisation cross section as a function of total energy gives an important overall check on theoretical methods for describing a collision. Total ionisation cross section experiments have also been performed with spin analysis, yielding the total ionisation asymmetry. 

The experimental data for hydrogen are compared with calculations in fig. 10.16. Both the convergent-close-coupling and coupled-channels-optical methods come close to complete agreement with experiment. The total ionisation cross section is a more severe test of theory, since it is an absolute quantity, whereas the asymmetry is a ratio. However, the correct prediction of the asymmetry reinforces the conclusion, reached by comparison with all other available experimental observables, that these methods are valid. 

Fig. 10.16. Total ionisation asymmetry for hydrogen. Open circles, Fletcher et al. (1985) squares, Crowe et al. (1990) full curve, convergent close coupling (Bray and Stelbovics, 1992b) crosses, coupled channels optical (Bray et al, 1991c).

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