Transcript of An Interview with the Molecular Physics Longuet-Higgins Young
Author's Prize Winner – 8th July 2014
Justin Robinson: I have the pleasure of speaking today with this year’s Molecular Physics LonguetHiggins Young Author’s Prize winner, Dr Lukasz Walewski, who is based at Ruhr-Universität Bochum in
Germany. His winning paper, as chosen by the editors from a strong field of 72 nominations, is
“Interaction-induced localisation of protons in hydrogen bonds at superfluid helium temperatures”
published in Volume 111, Issues 16-17 of Molecular Physics.
Lukasz, congratulations and thank you for speaking with me. How would you summarise your paper
for an undergraduate?
Lukasz Walewski: Well, atomic nuclei, being quantum particles, delocalize due to Heisenberg
uncertainty principle. This effect is the more pronounced the lower the temperature and the smaller
the mass of the nucleus. On the other hand interatomic interactions that make molecules out of
individual atoms counteract this tendency by confining the otherwise free particles. Our study shows
that these two competing effects result in a counter-intuitive behaviour of protons shared in
hydrogen bonds at superfluid helium temperatures of about 1 K. It turns out that these protons
undergo such a strong interaction-induced localisation that their effective size becomes smaller than
that of much heavier chlorine or oxygen atoms involved in the very same hydrogen bonds.
Justin Robinson: What are the practical implications of the research described in your paper?
Lukasz Walewski: Nuclear spatial distributions analysed in our paper are directly related to the
nuclear momentum distributions that - on the other hand - are accessible to deep inelastic neutron
scattering experiments, which makes a close connection between the theory and the experiment.
Moreover, the nuclear (de)localisation at cryogenic temperatures, which is the focus of our article,
might be relevant for many processes that take place in the interstellar space or terrestrial
stratosphere, such as formation of molecular hydrogen or ionization of simple acids.
Justin Robinson: How do you see your research area developing in the future?
Lukasz Walewski: So, low temperature phenomena, and particularly superfluidity, have been a
challenge to our understanding of nature since its discovery in the beginning of the 20th century.
Although a lot has been achieved in this field, many questions remain open, e. g. how chemical
reactions are possible at superfluid helium solvation conditions, where the usual thermal activation
is ineffective. Since nuclear quantum effects become increasingly important at such low
temperatures their investigations are expected to bring new insight into this and related problems.
Photoexcitation, on the other hand, is an alternative activation mechanism studied extensively at
normal conditions due to its relevance for living systems. The exploration of photoactivated reactions
at low temperatures including quantum effects is currently a developing field.
Justin Robinson: Who or what inspired you to get involved in this research?
Lukasz Walewski: My interest in quantum properties of atomic nuclei found in molecules was
initiated by Professor Piotr Bała, who pointed out that some aspects of chemical reactions might be
significantly affected by the resulting phenomena, e. g. the activation barriers can be significantly
reduced due to the zero point motion of the molecular skeleton. My further investigations of
correlated proton dynamics, performed under the supervision of Professor Bogdan Lesyng confirmed
the importance of nuclear quantum effects in proton transfer systems. The natural step forward was
to join the outstanding group of Professor Dominik Marx in Bochum who exposed me to the
fascinating issue of chemical reactivity at superfluid helium conditions, where these effects are even
more pronounced.
Justin Robinson: How did you feel winning the Molecular Physics Longuet-Higgins Young Author's
Prize and what does this mean to you?
Lukasz Walewski: It is my great pleasure to be selected as a winner of the Longuet-Higgins Young
Author's Prize. It is my first award of this kind and it feels simply great! The Prize honours an
important aspect of my recent research, which required long years of coding and development, and it
will certainly motivate me to continue scientific efforts in this direction. I feel particularly proud since
the results presented in the successful paper required quite an involved and non-standard data
analysis, which is now used by younger members of the group. However, this research would not be
possible without my senior co-author, Dominik Marx - it is my great honour to work with him.
Justin Robinson: Lukasz, thank you once again and all the best with your future endeavours.