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A University of Otago Professor from the Department of Physics has been awarded the 2023 Hector Medal by The Royal Society Te Apārangi.

The Hector Medal is awarded annually to a researcher for outstanding contributions to the advancement of chemical, physical, mathematical, or information sciences.

Niels Kjærgaard image
Professor Niels Kjærgaard.

Professor Niels Kjærgaard, who is also a Principal Investigator of the Dodd-Walls Centre, was nominated for his contribution to experimental studies of atomic collisions and light-scattering using ultracold gases.

“Coming from a different cultural background, it is heartwarming for my inner Viking to receive this New Zealand recognition for what my team has pulled off in the laboratory,” says Professor Kjærgaard, who originally hails from Denmark.

“This would not have been possible without ‘people, people, people’, joining in from all corners of the world and the land of the long white cloud to lend substance to Rutherford’s strong belief that ‘science should be international in its outlook and should have no regard to political opinion, creed, or race’.”

His research group is focused on quantum scattering, studying how ultracold atoms collide and how they interact with light. This research has enabled better understanding of the collective properties and behaviour of atoms in extreme states in which their motion is dominated by quantum mechanics.

Since coming to the University of Otago in 2010, Professor Kjærgaard has led the construction of an ultracold atom machine which uses powerful laser beams to create clouds of potassium and rubidium atoms at temperatures of less than a millionth of a degree above absolute zero.

He and his team have used this machine to study the scattering of light from atoms in these quantum gases, and the interactions between their atoms as they collide.

The award recognises more than a decade of work carried out by a team of skillful individuals greater than the sum of its parts, he says.

The news he had won was a “lovely recognition of our scientific merits and a welcome opportunity for me to reminisce about past adventures in the lab”.

“I am immensely honoured to have been at the helm on this tribe’s journey into the quantum world of atoms, and so proud of what loyal and collegial members of my group have achieved during the course of this and beyond.

“I hope that the award of the Hector Medal might help bringing our work to the attention of a wider Kiwi audience and stimulate interest in fundamental science and the scientific method, not least amongst young people.”

His group’s work follows on from studies pioneered by New Zealand’s most famous scientist, Ernest Rutherford.

In 2021, his group showed that ultracold temperatures suppressed the ability of the atoms to scatter light, making the gases more transparent. The research demonstrated and extended scientific understanding of the Pauli exclusion principle, which places fundamental constraints on where certain atomic particles can be located.

This blocking of light-scattering had been predicted 30 years previously, and his team’s experimental observations were published in Science magazine, and selected as one of the top-10 breakthroughs in 2021 by Physics World.

A referee for Professor Kjærgaard’s Hector Medal nomination says he has “performed unique and highly regarded experiments by controlling the collision parameters with exquisite precision, and has significantly advanced our understanding of the collisional processes”.

A further referee says, “Results like this require a consistent emphasis on excellence and the consolidation of experimental know-how.

Niels provides an outstanding example of how to succeed at the highest levels of science. He sets ambitious goals, maintains the highest standards of scientific rigour, and acts always with integrity and professionalism. He had made exceptional contributions to the field of ultracold atoms and has achieved international recognition for the work he has done in New Zealand.”

In 2021, Professor Kjærgaard co-edited a special issue of the Journal of the Royal Society of New Zealand marking the 150th anniversary of Rutherford’s birth and contributed a review paper on the scattering of indistinguishable particles in the quantum mechanical realm aimed at a non-specialist audience.

Journal of the Royal Society of New Zealand special issue: 150th anniversary of the birth of Ernest Rutherford

Effects of quantum mechanical identity in particle scattering: experimental observations (and lack thereof)
Journal of the Royal Society of New Zealand

Video: Professor Kjærgaard’s Inaugural Professorial Lecture

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