Direct view of atomic orbitals

Prabal K. Sinha, Puspitapallab Chaudhuri, Arnab Ghosh

In view of the recent interest in the trapping of antihydrogen atom $\mathrm{H}\ifmmode\bar\else\textasciimacron\fi{},$ at very low temperatures, $\mathrm{H}\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{-}\mathrm{H}$ scattering has been investigated at low incident energies using a close-coupling model with the basis set $\mathrm{H}\ifmmode\bar\else\textasciimacron\fi{}(1s,2s,2\overline{p})+\mathrm{H}(1s,2s,2\overline{p}).$ The predicted s-wave elastic phase shifts, scattering length, and effective range are in a good agreement with the other recent predictions of Jonsell et al. and of Armour and Chamberlain. The results indicate that the atomic orbital expansion model is suitable to study the $\mathrm{H}\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{-}\mathrm{H}$ scattering at ultracold temperatures.

Elisa De Ranieri

Eric R. Scerri

The main thrust of the paper involves a theoretical and philosophical analysis of the claim made in September 1999 that atomic orbitals have been directly imaged for the first time. After a brief account of the recent claims the paper reviews the development of the orbit and later orbital concepts and analyzes the theoretical status of atomic orbitals. The conclusion is that contrary to these claims, atomic orbitals have not in fact been observed. The non-referring nature of modern atomic orbitals is discussed in the context of Laudan's writings on realism, the success of theories, and whether or not scientific terms refer. I conclude that the failure to observe orbitals is a good prima facie case for divorcing the success of theories from the question of whether their central terms refer. The added relevance of this case is that it concerns a current and highly successful theory. Finally, the relevance of this ‘floating model’ to contemporary discussions on scientific models is briefly considered.

L I Ponomarev

“A naturalist, leaving the realm of direct sensory perceptions behind him with the aim of discovering more relationships, can perhaps be likened to a mountain-climber who wishes to reach the summit of the highest mountain to view the countryside stretched out before him in all its diversity. The mountain-climber must also leave the fertile populated valleys. As he ascends, he gains an ever wider view of the neighbourhood but, at the same time, the signs of life about him become less frequent. All the foregoing will have convinced people that an electron is not a point, it does not occupy a definite position in the atom, nor can it move in some orbit. In reality, everything turned out to be exactly the other way round: in the centre of the atom lies a tiny positive nucleus surrounded by a negative cloud of electrons. The atoms of various elements vary widely in nuclear mass and charge.

John Thomas