Based on quantum reactive-scattering theory, we propose a method for studyingthe electronic nonadiabaticity in collision processes involving electron-ionrearrangements. We investigate the state-to-state transition probability forelectron-ion rearrangements with two comparable approaches. In the firstapproach the information of the electron is only contained in the ground-stateBorn-Oppenheimer potential-energy surface, which is the starting point ofcommon reactive-scattering calculations. In the second approach, the electronis explicitly taken into account and included in the calculations at the samelevel as the ions. Hence, the deviation in the results between the twoapproaches directly reflects the electronic nonadiabaticity during thecollision process. To illustrate the method, we apply it to the well-knownproton-transfer model of Shin and Metiu (one electron and three ions),generalized by us in order to allow for reactive scattering channels. It isshown that our explicit electron approach is able to capture electronicnonadiabaticity and the renormalization of the reaction barrier near theclassical turning points of the potential in nuclear configuration space. Incontrast, system properties near the equilibrium geometry of the asymptoticscattering channels are hardly affected by electronic nonadiabatic effects. Wealso present an analytical expression for the transition amplitude of theasymmetric proton-transfer model based on the direct evaluation of integralsover the involved Airy functions.
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