Bjerrum length, polyelectrolyte-counterion interactions

Subdivision of counterions into condensed and uncondensed populations according to the Manning/Oosawa depiction is not unique. For example, a hypothetical thermodynamically bound counterion population can be defined to account for the deviations of polyelectrolyte solutions from thermodynamic ideality (35) this population is not equal to the condensed population. One can also use different definitions of condensed. The inflection point in the radial ion distribution, the Bjerrum length, and the radial distance over which the electrostatic interaction energy decays to kT have all been employed as alternative criteria for defining a condensed fraction (50). 

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