Mutual neutralization experiments with atomic and small molecular ions

Mutual neutralization is the process in which two singly charged atomic or molecular ions—one positive and one negative—interact and form two neutral particles by charge exchange.

Mutual neutralization is of interest as a fundamental charge-recombination mechanism, and it takes place in a variety of both naturally occuring and man-made plasmas.

As a fundamental process, mutual neutralization has been studied experimentally for several decades, but only very recently have experiments been realized, which are capable of determining the final quantum states in which the neutral particles are formed. Such experiments are extremely challenging and an absolute necessity to test and validate theory.

With stored ion beams in DESIREE, we reach control of the initial states as well, by natural decays or by laser manipulation, to study mutual neutralisation processes in unprecedented detail.

An experimental main aspect of the work proposed here is an active control of the initial quantum states by laser manipulation.

One of the applications, on which we focus in the present project, is mutual neutralization between hydrogen anions and positive ions in stellar atmospheres: The quantitative determinations of element abundances from observations relies on stellar atmosphere models where mutual neutralization is important, but where experimental data is badly needed.