The Lateral Distribution of Ions across the Track of an Ionizing Particle (Part I)

If Lea's (1947) picture of the lateral distributions of positive and negative ions across the track of an ionizing particle is correct, then there must be a radial electric field. Expressions are deduced for this field, the corresponding potential differences, and the energy per ion pair stored in the field. Numerical values are obtained for an ion density of 1000 ions per micron in water, hexane, and a chromosome thread. The field is of the order of 105 volts/cm. at relatively large distances from the axis of the track. An approximate expression is derived for the distribution of the positive and negative ions when in thermal equilibrium. Small ion densities can be in equilibrium with quite large separation of charge, but in the case of ion densities of 1000 ions per micron Lea's distributions are far from equilibrium, and the electrons would return to the positive core unless captured. If, when an ionizing particle passes radially across a chromosome, this separation of charge occurs, and the electrons become attached to the fabric of the chromosome, then tensions of the order 105 dynes/cm.2 would be produced normal to circles of radius comparable with that of the chromosome. A tension wave would travel in both directions away from the point of intersection of track and chromosome. If the chromosome has weak points, e.g., between genes, breaks might be produced here, and the minute deletions might be due to the two tension waves each producing a break. It is pointed out that Jaffé's (1913) initial distribution differed from Lea's in that both positive and negative ions were assumed to have the same parameter b. Also Jaffé's theory did not take account of the field which is created by the separation of charge produced by the external field, which for ion densities 1000 per micron can be very large. It is concluded that a value for b cannot safely be taken from Jaffé's work without further scrutiny.