# Review of Electron states in clusters

**1995-1996**. One of the main lines of investigations in the late 90▓s was concerned with clusters. Present-day technology makes possible creation of molecular clusters with a predetermined number of molecules. We developed a polaron theory of electron states in aqueous (**n < 110**) and ammonia clusters (**n < 1100**). For these clusters we achieved good agreement between theoretical and experimental data on electron photodetachment from a cluster. The polaron theory gave correct values for the critical number of molecules in a cluster at which a bound electron can form there. Solutions of polaron equations suggested a concept of an electron state within a cluster (interior cluster state) and an electron state on the cluster surface (surface electron state). It was shown that the bifurcation point at which solutions of both types coincide corresponds to the critical value of the cluster size at which cluster still can acquire a charge. The results obtained provide support for the view that polaron extended states can arise in clusters and in biomacromolecules.

The influence of an external magnetic field on the formation of charged clusters was studied. It was shown that a magnetic field gives rise to two effects: first, electron states stabilize themselves in a cluster, second, charged clusters of a subcritical size can form. A possibility of experimental testing of the results obtained is being discussed.

Besides the cluster subject-matter, theoretical studies of polaron and bipolaron states in various chemical and physical systems were continued.

**1996-1998**. Based on the polaron theory developed, we calculated interior and surface electron states in clusters. It was shown that there is a critical cluster size at which a bound state of an electron and a cluster can form.

An approach to calculation of clusterization effects was developed and applied to an excess electron in inert gas.

**1998-2000**. Electron states were calculated in charged polar crystals containing an ion of alcali metal. Experimental evidence on electron photodetachment from charged polar clusters was interpreted in terms of the F-center model. An approach to calculation of multicharged polar clusters was developed.

**2000-2005**. Considerable study was given to calculation of electron states in molecular clusters. Electron states in polar clusters were simulated with the help of the polaron model. It was shown that the electron model without regard for image forces in a cluster explains perfectly well the long-wave part of the absorption spectrum aqueous and ammonia clusters. At the same time, to calculate the short-wave part, consideration of the image forces is required.

With this in mind we calculated electron states in a polar cluster with due regard for the image forces. It was shown that taking account of the image forces gives rise to new branches in the electron spectrum of charged polar clusters.

Some work was done to understand the interaction between proteins using information on their hydrophobic and electrostatic potential, which can be derived from their known or simulated 3D structure.