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Journal of Physics B: Atomic, Molecular and Optical Physics TOPICAL REVIEW • OPEN ACCESS Computational treatment of electron and photon collisions with atoms, ions, and molecules: the legacy of Philip G Burke To cite this article: Klaus Bartschat et al 2020 J. Phys. B: At. Mol. Opt. Phys. 53 192002 View the article online for updates and enhancements. This content was downloaded from IP address 193.60.240.99 on 23/09/2020 at 14:36 Journal of Physics B: Atomic, Molecular and Optical Physics J. Phys. B: At. Mol. Opt. Phys. 53 (2020) 192002 (21pp) https://doi.org/10.1088/1361-6455/aba473 Topical Review Computational treatment of electron and photon collisions with atoms, ions, and molecules: the legacy of Philip G Burke Klaus Bartschat1 , Andrew Brown2 , Hugo W. van der Hart2, James Colgan3,6 ,NSScott4 and Jonathan Tennyson5 1 Department of Physics and Astronomy, Drake University, Des Moines, IA 50311, United States of America 2 Centre for Theoretical Atomic, Molecular and Optical Physics, Queen’s University Belfast, Belfast, BT7 1NN, United Kingdom 3 Los Alamos National Laboratory, Los Alamos, NM 87545, United States of America 4 Engineering and Physical Sciences, Queen’s University Belfast, Belfast, BT9 5BN, United Kingdom 5 Department of Physics and Astronomy, University College London, WC1E 6BT, London, United Kingdom E-mail: [email protected] Received 6 April 2020, revised 26 May 2020 Accepted for publication 9 July 2020 Published 24 August 2020 Abstract This review summarizes the path-breaking contributions of Philip George Burke (1932–2019) to atomic, molecular, and optical physics, in particular the computational treatment of electron and photon collisions with atoms, ions, and molecules. Keywords: electron collisions, photoionisation, R-matrix, Burke (Some figures may appear in colour only in the online journal) 1. Introduction: overview of Philip George Burke’s Exeter, where he read physics, graduating in 1953. Phil under- career took a PhD at University College London (UCL), submitting a thesis in 1956 entitled, ‘A theoretical investigation into the The son of Henry and Frances Mary (Sprague) Burke, scattering of nucleons by light nuclei and the nature of nuclear Philip George Burke, shown during the 2011 International forces’. He worked under the supervision of Sir Harry Massey Conference on Photonic, Electronic, and Atomic Collisions FRS and Professor R A Buckingham. (ICPEAC) in Belfast in figure 1, was born in London on Octo- In 1956, Phil was appointed to a Research Fellowship at ber 18, 1932. He lived in London during the Second World UCL, where he was given the opportunity to use the pilot ACE War Blitz, and memories of the bombings were still fresh in and DEUCE computers at the National Physical Laboratory his mind when one of us (NSS) last reminisced with him in (NPL) at Teddington. Here he interacted with Dr H H Robert- September 2018. He attended the University College of the son and Dr J H Wilkinson, jointly publishing a paper with South West of England, later to become the University of Robertson (Burke and Robertson 1957), on low-energy elastic 6 Author to whom any correspondence should be addressed. scattering of neutrons by deuterons. Original content from this work may be used under the terms In 1957, Phil was appointed Assistant Lecturer at the newly- of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title formed Computer Unit of the University of London, which was of the work, journal citation and DOI. headed by Professor R A Buckingham. Here he engaged in 0953-4075/20/192002+21$33.00 1 © 2020 The Author(s). Published by IOP Publishing Ltd Printed in the UK J. Phys. B: At. Mol. Opt. Phys. 53 (2020) 192002 Topical Review Phil’s second atomics physics paper was with Harry Schey (Burke and Schey 1962). It focused on the topic of low-energy elastic scattering of electrons by atomic hydrogen, a problem introduced to Phil by Dr Mike Seaton at UCL, and involved the use of an IBM 709. The comment in the paper that, ‘this work was undertaken to bring to bear upon this problem cal- culational opportunities placed at the disposal of theorists by modern computing facilities, in the hope that certain discrep- ancies between theory and experiment may be resolved by the nearly exact solutions now possible’, established a rationale that pervaded all of Phil’s future work. In the UK, toward the end of 1956, joint Atomic Energy Authority/Civil Service Commission Boards (Hoff Boards) were established to stem the ‘brain drain’ and recruit emigr´e scientists back to the UK. Phil was recruited in 1962 and took up an appointment as Research Fellow, later Senior Princi- pal Scientific Officer, in the Theory Division at the Atomic Energy Research Establishment at Harwell. Phil continued his research in particle physics in collaboration with scientists at the Rutherford Appleton Laboratory and in atomic physics in support of the plasma physics programme at the Culham Laboratory. In this work he used the recently acquired IBM STRETCH computer at AWRE, Aldermaston. This produc- Figure 1. Phil Burke at the 2011 ICPEAC in Belfast. tive time included a series of four papers on low-energy elec- tron scattering by atomic hydrogen, published back-to-back in 1967 (Burke et al 1967a, Taylor and Burke 1967,Burkeet al computational atomic and nuclear collision research using the 1967b, Macek and Burke 1967). newly installed Ferranti Mercury computer. This enabled Phil Following the departure of Professor Alex Dalgarno FRS to develop further his interest and expertise in the emerging from Queen’s University Belfast to the Harvard College field of scientific computing. Observatory and Smithsonian Astrophysical Observatory, Phil In 1959, Phil married Valerie Martin, then a research stu- was appointed to the Chair of Mathematical Physics at Queen’s dent at UCL, and they went to work at the Lawrence Radiation University Belfast on the 1st November 1967. He delivered Laboratory in Berkley, California. Here Phil had access to IBM his inaugural lecture on 11th December 1968 on the topic 704, 709, and 7090 machines, which were far superior to any entitled ‘Particles and resonances in modern physics’. At the machines in the UK, and he was able to develop code in FOR- start of the lecture he commented that this topic for discus- TRAN rather than machine code. Phil was initially employed sion was chosen because it provided ‘...somesortofunifying in the preparation and analysis of experiments on the 72 inch link across several branches of physics...itisalsoonewhich hydrogen bubble chamber, under the general direction of Pro- I believe enables a common language and a common appre- fessor Louis Alvarez. After that he joined the Theory Division, ciation to be developed for branches of physics as diverse as where he carried out research in computational atomic and the properties of liquids and solids at almost zero temperatures, particle physics. the behavior of atomic nuclei in the interior of stars, the behav- Phil’s first paper in atomic physics was in collaboration ior of gases at high temperatures, and the understanding of the with Ken Smith at Argonne National Laboratory (ANL). In interaction of matter under the acceleration of billions of volts’ Smith and Burke (1961) they examined the effect of virtual (Burke 1968). excitations on the elastic scattering of electrons and positrons Phil joined the Department of Applied Mathematics and by atomic hydrogen. The numbers reported were obtained Theoretical Physics, which was headed by Professor (later through the use of an IBM 704 at ANL. This paper marked the Sir) David Bates FRS. Interestingly, both had had their early start of Phil’s enormouscontribution to the study of resonances careers shaped by Professor Sir Harry Massey FRS. Alan Hib- in atomic and molecular scattering. The following comment in bert, who joined Queen’s a few weeks after Phil, recounts in the paper also testifies to Phil’s early recognition of the need Scott et al (2020) that he ‘quickly established a small research to develop general rather than one-off special-purpose codes: group...withtheaimofconstructingrobustandgeneralpro- ‘A generalized version of the program used to calculate the grams to enable both atomic structure and atomic collision numbers reported here has been written and is being tested. processes to be calculated’. With this program we hope to calculate...thetotalelasticcross From 1977 to 1982 Phil held a joint appointment with section in the strong-coupling exchange approximation over Daresbury Laboratory, in Cheshire, where he was Head of the entire energy region and so be able to compare the results the Theory and Computational Science Division. With typi- with the experimental results of Bederson et al and Brackman cal devotion to duty, as recalled by Alan Hibbert in Scott et al et al’. (2020), ‘he maintained his teaching and research commitments 2 J. Phys. B: At. Mol. Opt. Phys. 53 (2020) 192002 Topical Review in Queen’s by traveling, every week in term time, on the Liver- was elected to membership of the Royal Irish Academy in 1974 pool–Belfast boat—on Wednesday night from Liverpool and and to Fellowship of the Royal Society of London in 1978; he returning on Friday night. He spent the days in Belfast under- was awarded the Institute of Physics’ Guthrie Medal and Prize taking his undergraduate teaching and meeting graduate stu- in 1994 and the David Bates Prize in 2000; he was recipient of dents and colleagues’. One of us (NSS) can attest to this, as he the American Physical Society Will Allis Prize in 2012. Phil was one of Phil’s PhD students at the time. was appointed as a CBE in the 1993 Queen’s Birthday Honors During his 40+ years at Queen’s, Phil developed fur- for services to science.

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