Theis, J; Reinhardt, J; Muller, B, *How good is the adiabatic basis in heavy ion collisions?*,
Journal of the Physics B: Atomic and Molecular Physics, vol. 12 no. 16
(1979),
pp. L479-L483 [doi] .
**Abstract:**

*Discusses the optimal choice of the basis for calculations of inner-shell excitations in the collision of heavy ions. Starting from a variational principle which minimises the time-integrated coupling strength, a relation between a model two-centre distance and the actual internuclear separation is derived. For 1s sigma excitations in Pb-Pb collisions it is found that the optimal basis is almost identical to the adiabatic one. For higher quantum states the adiabatic treatment becomes less adequate.*