Schonland Colloquia - 2004


Prof Christian Toepffer  -
Cooling and heating of channelled ions
Wednesday 25th  November
at 10-15 after tea.
in the Schonland lecture hall.


Channeled ions can be cooled or heated with respect to their transverse energy under certain conditions. A phenomenological model which presumes different radii (impact parameters) for capture and loss of electrons by the channelled projectile is able to provide a description of the effect. However, previously, there was no prediction based on theoretical insight into atomic physics processes occuring during channelled ion motion which could illuminate the ideas of different capture and loss radii.

This talk is part of the sabbatical work of Prof Toepffer.

It develops for the first time a model which is able to account for the features of heating and cooling based on capture and loss radii as discussed above. The model is based on an explicit formulation of the cross-sections for charge exchange using a reparameterisation
of the effective charge and the quantum numbers to account for real atomic and molecular orbitals for the projectile and target respectively, as compared to hydrogenic wave functions. The model has proved remarkably robust and predictive.

This model will be used in the analysis of planned experiments at the Schonland to study heating and cooling of channelled ions at the Tandem Accelerator of the Schonland Research Centre.

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