Is it Possible to Observe Orbitals? On the Problems of Observability and Reality of Theoretical Entities

Abstract

In September 1999 "Nature" magazine announced that atomic orbitals were di-rectly observed. Opposing it, Eric Scerri, editor-in-chief of "Foundations of Chemistry", claimed that what could be observed in the experiment was electron density, not orbitals. The main purpose of this paper is to consider philosophical and methodological aspects of the above controversy. Especially, the problems of direct observability and reality of theoretical entities are taken under detailed discussion. From the point of view of quantum mechanics there are not any reasons to believe that orbitals exist. However, realistically treated orbitals are very effective tools in the laboratory practice of chemistry.