CHARLES STRACHAN MA(Aberd, Cantab), PhD(Cantab)

Charles Strachan was born in on 7 May 1907, the son of Edward A Strachan who was a bakery proprietor in the city. Education at Aberdeen was followed by his entry in 1925 to the as first bursar in mathematics and natural philosophy. This was the start of a close participation in the life of the University which continued, with some important but relatively short periods spent elsewhere, beyond his retirement in 1977 from his Readership in Natural Philosophy, until shortly before his death in Aberdeen on 21 September 1993. One could hardly have chosen a more auspicious year than 1925 to start on a lifetime in physics. The quantum ideas which dominated physics were on the point of making great advances. In Aberdeen, G P Thomson as Professor of Natural Philosophy was engaged in work that would make a key contribution to the experimental basis of quantum physics and that would earn him a Nobel Prize. Elsewhere, the same period saw dramatic theoretical developments which were to play a key part in Charles Strachan's career. Quantum ideas were being shaped into a mathematical theory which could be applied to a vast range of hitherto intractable problems. Charles Strachan was to be among the young mathematical physicists who seized on the opportunities thus offered. He duly completed his undergraduate work in Aberdeen with a First Class Honours degree. At that time it was standard practice in Scottish universities for the best graduates aiming at an academic career to read for a further undergraduate degree at Oxford or Cambridge. G P Thomson arranged for him to go to Thomson's former Cambridge College (Corpus Christi), where he undertook an accelerated tripos, attending courses by such great names in relativity and quantum theory as Eddington and Dirac. Charles Strachan achieved the distinction of becoming Junior Wrangler. He then embarked on research at Cambridge, first under R H Fowler and then under J E Lennard Jones, and was awarded a Cambridge PhD in 1935. Prominent among his pre-war researches were investigations, the earliest in collaboration with Lennard Jones, of the interaction of atoms and molecules with solid surfaces. These papers brought out some important quantum effects in the behaviour of systems of many atoms and presented mathematical procedures which made possible the application of quantum mechanics to the quantitative treatment of these effects. They represented significant early contributions not only to surface physics but more generally to aspects of solid state physics which are still the subject of extensive investigation. Part of this work was done at Aberdeen, where he held an assistantship and then a lectureship between 1933 and 1937. In 1937 he was invited by Professor Max Born to take up a temporary lectureship for one year in his Department in and he clearly decided that the opportunity of working with this very great theoretical physicist could not be missed. From 1938 to 1946 he was lecturer in Applied Mathematics at the University of Liverpool, being acting Head of Department during Professor Rosenhead's absence from 1939 to 1945. In 1946 he was appointed Senior Lecturer in Natural Philosophy at Aberdeen, where he was now to remain, shortly after Professor R V Jones was appointed to the Chair of Natural Philosophy. He embarked at once on the exciting if somewhat daunting task of teaching mathematical physics to large Junior and Senior Honours classes in which students returning from the forces were in a majority. These and subsequent undergraduates in both physics and engineering received tremendous benefits from the experience Charles Strachan had acquired and the enthusiasm he maintained for his subject. He is remembered by his students for mental sharpness, his warmth, his humanity and the good humour with which he nurtured even the struggling. His post-war researches at Aberdeen were varied as regards both the topics investigated and the theoretical methods involved. They extended to an investigation of how spin-orbit coupling could account for anomalous features of the Hall effect in ferromagnets but most were concerned with topics in nuclear physics. His nuclear investigations commenced with studies of aspects of β-decay, a subject on which he published in 1969 a book The Theory of β-decay in which he edited and introduced a collection of classic papers. He moved on to treat the scattering of high energy electrons by nuclei and followed this with studies of electro-disintegration in which a proton or a neutron is ejected from the nucleus by electron impact. I am indebted to Dr A Watt of Glasgow University, who was one of his research students, for pointing out Dr Strachan's prescience in the importance of this last topic, which is still not completely understood and is currently the principal area of research for electron accelerators in nuclear physics. He inspired a succession of research students who worked with him on most of these topics. Charles Strachan's interests were many but particularly mention must be made of his music. He was an excellent pianist but he decided that full participation in the musical life of the University and the Town required mastering an orchestral instrument and he took up the bassoon. He subsequently led the bassoon section of the orchestra and hit an unexpected height in bassoon playing when the bassoonist of Liverpool Music Group took ill shortly before a concert in the Cowdray Hall, whereupon Charles stood in for him with what one person present described as 'aplomb'. That was an occasion on which aplomb was very appropriate but in the ordinary course Charles Strachan was the most modest of people. He will be remembered by those who knew him, and there are many, for his modesty, for his kindness and for his strong attachment to his family. Colleagues in the Department and on Committees benefited greatly from his knowledge and wisdom, and the benefit of his good sense was for some time spread more widely by his work for the Samaritans. He extended a warm welcome to all who came into his circle of acquaintance and took pleasure in the many friendships which resulted. Nowhere was this more true than in the University Common Room where his almost daily visits extended over so many years. He was elected to Fellowship of the Royal Society of Edinburgh in 1942 and served on its Council from 1969 to 1972. His wife Marion, also a physicist, whom he married in 1939, died in 1971. He is survived by his second wife Nancy, whom he married in 1973, and by his son Edward and daughters Molly and Marion. I am indebted to Dr John S Reid of the University of Aberdeen who collaborated with me on an earlier version of this obituary.

C W McCOMBIE