Minimum ionisation potentials

In previous sections, we have, for simplicity, confined our attention to situations involving one open channel. For isolated Fano profiles, this leads to an exact zero in the cross section at the transmission window, and to a series of exact zeros in the cross section associated with each resonance for a complete Rydberg series. Obviously, if one wishes to study profile shapes in detail and the connection between the bound states and autoionising resonances implied by Seaton s theorem (see previous section) it is desirable to work just above the first ionisation potential, where the number of open continuum channels is at a minimum. In general, this is not possible, and the number of open channels increases rapidly with increasing energy. 

Monolayer properties of octadecyldimethylamine oxide alone and in combination wth sodium alkyl sulfate on aqueous substrate have been investigated. Nonionised amine oxide produces more expanded film than the ionised species minimum film expansion and highest surface potential are obtained at half ionisation. 

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