Professor Igor Bray is the head of Physics, Astronomy and Medical Radiation Science at Curtin University. His research focuses on atomic collision theory, and he codeveloped the Convergent Close-Coupling Theory, which is important for unifying the theoretical treatment of electron-atom collisions at all energies, for both excitation and ionization processes. He is also widely involved in science communication and science advocacy. As he explains below, Professor Bray believes the lessons of science are important in all aspects of life.
Q: Which research projects are you and your group currently working on?
- Antihydrogen formation via the charge-exchange process in excited positronium Ps(n) scattering on antiprotons. We found that for n=3 the cross sections of antihydrogen formation are particularly large. With modern-day laser-excitation techniques Ps can be formed in much higher n-states. It is tempting to assume scaling procedures will provide monotonically increasing estimates. However, the degenerate nature of the energy levels leads to enormous elastic cross sections as well. How these will couple to the desired charge-exchange cross sections is the problem of current interest.
- Charge exchange processes are rather ubiquitous in positive ion scattering on atoms and molecules. An application of immense importance is in ion therapy, which utilises the Bragg peak for delivering the destructive energy to just the targeted tumour. This requires careful calculation of ion stopping power with molecules of biological relevance. Having developed efficient ion-atom scattering theory we are working towards molecular targets.
- There has been great progress in the field for relatively simple quasi one- and two-electron atomic targets. The next challenge is to increase the complexity of the targets to multi electron atoms and molecular systems. We’ve recently made considerable progress with implementation of the molecular hydrogen target, and the challenge now is to extend this to more complex molecules.
Q: What motivated you to pursue this field of research?
Pure coincidence! My PhD is entitled “Gravitational Lens Effect of Galaxies and Black Holes”, from the University of Adelaide in South Australia. I came across to Flinders University, also in Adelaide, as a research assistant during the writeup of my PhD. There I came across Professors Ian McCarthy and Erich Weigold who offered me a five-year postdoctoral position. Having researched the field and found that the validity of the existing computational methods depended on the incident projectile energy, and that there were still discrepancies between theory and experiment for the e-H scattering problem, I thought that there was an opportunity for me to contribute. The convergent close-coupling (CCC) method was developed with this in mind.
Q: Where do you think the field is heading?
The recent progress in the field of Quantum Scattering Theory has been spectacular. What used to be separate computational techniques for excitation and ionization processes, which varied with projectile energy, are now able to be routinely calculated with a single computational method. Formal problems with the definition of scattering amplitudes in the case of breakup collisions have also been resolved. This creates a solid foundation for further progress towards more complicated multi electron collision systems whose solutions are required in practical applications.
Q: What current problem facing humanity would you like science to provide a solution to?
The greatest contribution of science to humanity is not its technical progress and utility, but its culture. Science is collaborative, cooperative, based on evidence, and constructive contributors are welcome irrespective of their gender, ethnicity or nationality. The challenge is to get all of humanity to embrace such a culture, and this means that scientists, and that includes science teachers, must be more visible and valued at all levels of society.
Q: What interests you outside of science?
I take my culture of science to everything I do, and use it to understand everything I see, which includes human behaviour. I have a public lecture entitled “The Physics of Politics”, where I look at contemporary issues through the eyes of a physicist. For example, the complexity of gun control can be viewed through the perspective of an unstable equilibrium (or mutually assured destruction (MAD)). Understanding this means that any transition to a stable equilibrium requires small steps on both sides. The Laws of Physics arise from symmetry principles as do the Laws of humanity such as the “Golden Rule” of treating others like we’d like to be treated ourselves. Entropy increases, or equivalently, Information is lost, manifesting itself by leading to reduction over time in quality or standards. To counteract this requires constant external effort.
Q: What do you find to be the most rewarding aspect of your job?
For the past three decades I have had the pleasure of enjoying research success, initially due to personal effort and then mostly as part of a team. This has been a fantastic ride, and continues to be so. Following the birth of my two children I have added to my job outreach activities in primary and high schools. Seeing the enthusiasm for science of younger generations is highly energising. During the last six years I have had the pleasure of being Head of Physics, Astronomy and Medical Radiation Science at Curtin University. Though this comes with its unique challenges, the opportunity to build a strong research-active group of outstandingly talented people who are also outstanding teachers has been particularly rewarding.
On behalf of JPhysB I would like to thank Professor Bray for answering our questions and for recently publishing Solution of the proton-hydrogen scattering problem using a quantum-mechanical two-center convergent close-coupling method in Journal of Physics B. You can also find out more about his research here.
Read more of Professor Bray’s recent work:
- Calculations of electron-impact ionisation of Fe25+ and Fe24+ published as part of a special issue on Atomic and Molecular Data for Astrophysics
- Accurate solution of the proton–hydrogen three-body scattering problem
- Relativistic convergent close-coupling calculation of spin asymmetries for electron-indium scattering
- Negative ion resonance measurements in the autoionizing region of helium measured across the complete angular scattering range (0°–180°)
This work is licensed under a Creative Commons Attribution 3.0 Unported License
Image 1 and front image: copyright Igor Bray; used with permission.
Categories: Journal of Physics B: Atomic, Molecular and Optical Physics