Could you explain the significance of your article to the non-specialist?

The concept of the solvated electron is one of the most fascinating issues in solution chemistry. Originally invented to explain the unusually low lying optical spectra of alkali metal solutions in liquid ammonia and water, it turned out to be a viable theoretical tool even in modern quantum mechanical calculations to explain most of the experimental data. A new step forward was obtained by studying the behaviour of negatively charged or neutral doped clusters of ammonia and water as function of their size which allows us to get an explanation of the phenomena at the microscopic level. We added the interaction of sodium with methanol clusters and compared it with the results already obtained for water and ammonia clusters.

What has motivated you to conduct this work?

Molecular beam experiments with cold clusters provide a microscale exploration of the phenomenon of the solvated electron. Until now a large number of experimental and theoretical studies have focussed on water and ammonia microsolutions. Methanol received much less attention though it builds complexes with a much simpler topology compared to water. The exploration of the methanol system helped us to identify differences but also common motives of the alkali electron solvation in water and ammonia.

Where do you see this work developing in the future?

The main result of our study was the similarity of the methanol data with water but the appreciable differences compared to ammonia. Therefore a natural extension of the present work would be to investigate solvents like methylamine and ethanolamine which contain characteristic groups of both systems. In addition, the measurements can be extended from obtaining the data for the ionization potentials to the infrared spectroscopy which became recently available for these systems. This should give complementary results.

Are there any particular challenges facing future research in this area?

The challenges of the future research in this area are twofold. First the problem of surface and interior states of the solvated electron or better the transition from the surface to the interior state at a particular size has to be clarified. Here many experiments and also calculations still disagree. The other problem is a definite explanation for the striking difference in the behaviour of water/methanol and ammonia. There are numerous, partially converging models in the literature, but a clear cut proof is missing.