Tunneling induced electron transfer between separated protons

TL;DR

This paper investigates electron transfer between separated protons using local control theory, demonstrating near-unity transfer efficiency via tunneling with tailored pulse sequences, and analyzing the impact of nuclear motion on transfer success.

Contribution

It introduces a method to control electron tunneling between protons with optimized pulse sequences and studies the effects of nuclear motion on transfer efficiency.

Findings

High transfer efficiency achieved with pump and dump pulses.

Tunneling occurs on femtosecond timescales.

Nuclear wave function spreading reduces transfer yield.

Abstract

We study electron transfer between two separated nuclei using local control theory. By conditioning the algorithm in a symmetric system formed by two protons, one can favored slow transfer processes, where tunneling is the main mechanism, achieving transfer efficiencies close to unity assuming fixed nuclei. The solution can be parametrized using sequences of pump and dump pi pulses, where the pump pulse is used to excite the electron to a highly excited state where the time for tunneling to the target nuclei is on the order of femtoseconds. The time delay must be chosen to allow for full population transfer via tunneling, and the dump pulse is chosen to remove energy from the state to avoid tunneling back to the original proton. Finally, we study the effect of the nuclear kinetic energy on the transfer efficiency. Even in the absence of relative motion between the protons, the spreading of the nuclear wave function is enough to reduce the yield of electronic transfer to less than one half.