Jim Mitroy

James (Jim) Dumitru Mitroy, Professor in Physics at Charles Darwin University in the Northern Territory of Australia, unexpectedly passed away on August 28th, 2014 at the age of 57. Best known for his proof of the existence of positronic atoms, Jim published nearly 200 papers, and was still in full scientific flight at his end. A creative scientist with incredible capacity for work, Jim was one of the most formidable theoretical atomic, molecular and optical physicists of his generation.

Jim was born in Toorak, Melbourne on the 16th February 1957, to Nicolae Mitroi, a post-World War II refugee from Romania, and the late Dora Steele, a fourth generation Australian. Raised in a family of modest means, he won scholarships to attend The University of Melbourne. He received a first-class honours degree, and completed a PhD there on studies in atomic structure and (e,2e) reactions between 1978-1983 under the supervision of Ken Amos. He took up postdoctoral research associate positions, first at Flinders University (1983-1986) with the late Ian Ellery McCarthy, then at JILA (1986-1988) with David W. Norcross, and thirdly as a Research Fellow at the Australian National University (1988-1989).

In 1989 Jim was hired as a lecturer by the fledgling University College of the Northern Territory in Darwin. The U.C.N.T. became the Northern Territory University and then Charles Darwin University. Along with the two other physics lecturers there, Jai Singh and Steve Shanahan, Jim was instrumental in establishing an undergraduate physics programme (which was short-lived due to the small number of physics students in the Northern Territory). Jim’s distinctive manner of personal deportment was noted by all, and won him many fast friends. Jim managed to mostly avoid becoming, as he called it, ‘a suit’. Amongst his most enjoyable such roles, however, was when helping graduate students as the Associate Dean of Research and Postgraduate Studies and as the University’s representative on the Australian Council of Deans and Directors of Graduate Studies and the Australian Institute for Nuclear Science and Engineering.

In the early 1990‘s Jim began working on antimatter-matter interactions, the subject of his most noteworthy contributions to physics. On sabbatical with Andris Stelbovics at Murdoch University in 1993, Jim published a series of computational solutions to the collisions of positrons with atoms. His most striking physics discovery was that of positronic atoms. These atoms consist of positrons stably bound to neutral atoms (wherein they will eventually annihilate), analogous to negative ions where an electron is bound to a neutral atom. Although previous studies had suggested this possibility (especially in 1995 by the group of Victor Flambaum at the University of New South Wales), in 1997 Jim and his postdoc Gregory Ryzhikh used a computer program developed by Kalman Varga to unexpectedly, yet variationally, prove the existence of positronic lithium. Coincidentally, Krzysztof Strasburger and Henryk Chojnacki at the Wrocław University of Technology submitted a paper 19 days earlier proving the same result! This subject remains of current interest because, as of early 2015, no positronic atom has yet been seen in experiments. Jim was a core member of the Australian National Centre of Excellence for Antimatter-Matter Studies, which ran during 2006-2013, and he contributed broadly to its success.

In the past decade Jim moved relentlessly into studying photon-atom and atom-atom interactions, and was in the process of developing a website with a compilation of the massive data sets (see http://www.smp.uq.edu.au/people/brom/atomfoundry/vdwwww/ ). He was the leader of two separate collaborations that led to major review articles, one on atomic polarizabilities in 2010 and another on explicitly-correlated Gaussian basis functions in 2013. He had recently developed a fruitful scientific partnership involving regular visits to the atomic physics group of Ting-Yun Shi and Li-Yan Tang at the Wuhan Institute of Physics and Mathematics in Wuhan, China, whose hospitality he enjoyed immensely.

Jim was an idiosyncratic and sparkling character. He was first and foremost a consummate scientist who would not stand for anything but the best - and as many will attest, he took us to task when he thought we had things wrong or could do things better. He had a unique approach to educating his experimental colleagues - a combination of banter, badinage, and strangely appropriate Australian colloquialisms. He particularly liked to deliver his assessments to the students with a pointed, but always entertaining, twist. Jim’s insight, formidable intellect, persistence, scientific rigour and wit will be sorely missed by all those colleagues who knew him.

Michael W.J. Bromley
School of Mathematics and Physics
The University of Queensland

Stephen J. Buckman
Research School of Physics and Engineering
Australian National University

Charles W. Clark
Joint Quantum Institute, National Institute of Standards and Technology
and the University of Maryland.