Announcement of the winner of the Longuet-Higgins Early Career Researcher Prize 2021

ABSTRACT

The reactions between ground state ${\mathrm{H}}_2^{+}(\mathrm{X}{}^2{\mathrm{\Sigma }}_g^{+}(v=0,J=0))$ and ${\mathrm{D}}_2$ forming ${\text{HD}}_2^{+}+\text{H}$ and ${\text{H}}_2{\text{D}}^{+}+\text{D}$ were investigated in the range of collision energies $E_{\mathrm{coll}}$ between $E_{\mathrm{coll}}/k_{\mathrm{B}}=0$ and 10 K using a merged-beam approach. The reaction rates measured experimentally are compared to those obtained for the reaction between ${\text{H}}_2^{+}$ and ${\text{H}}_2$ forming $H_3^{+}+H$ under similar experimental conditions. Below 1 K, a clear enhancement of the reaction rate coefficient compared to the Langevin rate measured at higher collision energies was observed in both reaction systems. This enhancement is interpreted as originating from the interaction between the charge of ${\text{H}}_2^{+}$ and the quadrupole of para ${\text{D}}_2$ and ortho ${\text{H}}_2$ molecules in the J = 1 rotational level. The enhancement of the reaction with ${\text{D}}_2$ was found to be significantly less than that of the reaction with ${\text{H}}_2$, reflecting the relative population of the J = 1 rotational level of ${\text{H}}_2$ (75%) and ${\text{D}}_2$ (33%) in natural samples at low temperatures. Simulations of the experimental results based on the theoretical predictions of the reaction cross sections by Dashevskaya et al. [J. Chem. Phys. 145, 244315 (2016)] reveal agreement within the experimental uncertainties. The branching ratio η of the reaction involving ${\text{H}}_2^{+}$ and ${\text{D}}_2$ and forming ${\text{H}}_2{\text{D}}^{+}$ and $\text{D}(\eta =\frac{[{\text{H}}_2{\text{D}}^{+}]}{[{\text{H}}_2{\text{D}}^{+}]+[{\text{HD}}_2^{+}]})$ near E_coll = 0 was determined to be 0.341(15). Time-of-flight measurements of the velocity distributions of the reaction products are compatible with an isotropic product emission with an average total kinetic energy of 0.45(5) eV for both channels, representing about 30% of the total energy released by the reaction.

GRAPHICAL ABSTRACT

The Editors of Molecular Physics are pleased to announce that the winner of this year's Longuet-Higgins Early Career Researcher Prize is Katharina Höveler, Laboratory of Physical Chemistry, ETH Zurich, Switzerland, for her excellent work as part of the author team Katharina Höveler, Johannes Deiglmayr, and Frédéric Merkt. Deviation of the rate of the $H_2^{+}+D_2$ reaction from Langevin behaviour below 1∼K, branching ratios for the ${HD}_2^{+}+H$ and $H_2{D}^{+}+D$ product channels, and product-kinetic-energy distributions. doi:10.1080/00268976.2021.1954708. Article: e1954708. [1]

This year the Editors reviewed the entire 2021 volume 119 of Molecular Physics, selecting from among the eligible papers those which best met the criteria for the prize at the annual Editors’ Board Meeting. The candidates encompassed both experimental and theoretical approaches and underlined the exciting science being published in Molecular Physics across all fields covered by the journal: quantum chemistry and electronic structure theory; chemical dynamics, photo physics and spectroscopy; spin resonance; statistical mechanics of liquids, soft matter and complex systems.

The Longuet-Higgins Early Career Researcher Prize Winner 2021

Katharina Höveler, Laboratory of Physical Chemistry, ETH Zurich, Switzerland

Katharina Höveler, Johannes Deiglmayr & Frédéric Merkt. Deviation of the rate of the $H_2^{+}+D_2$ reaction from Langevin behaviour below 1∼K, branching ratios for the ${HD}_2^{+}+H$ and H₂D⁺ + D product channels, and product-kinetic-energy distributions. doi:10.1080/00268976.2021.1954708. Article: e1954708. [1]

The Longuet-Higgins Prize article by K. Höveler et al. reports on an investigation of the ultralow-temperature kinetics of the ${\text{H}}_2^{+}+{\text{D}}_2$ ion-molecule reaction which is of prime importance in astrochemistry. At collision energies below 1 K, a pronounced deviation of the reaction rate constant from the Langevin model, which often serves as the ‘gold standard’ in ion-molecule chemistry, was observed. This discrepancy was attributed to charge-quadrupole interactions which become important in this collision system only at very low temperatures. The experiments relied on an elegant, recently developed merged-molecular-beam method using H₂ Rydberg molecules instead of bare ${\text{H}}_2^{+}$ ions. This approach was crucial to achieve the unprecedentedly low collision energies reported for the title reaction in this work, thus defining a new frontier in reaction-dynamics studies.

A profile of the winner, Katharina Höveler will be published in a forthcoming issue of Molecular Physics.

In addition to the Longuet-Higgins Early Career Researcher Prize, and in recognition of the excellent science behind these papers, the Editors have further awarded two Molecular Physics Early Career Researcher Prizes to P. Bryan Changala and Tarak Karmakar

Molecular Physics Early Career Researcher Prize Winner 2021

P. Bryan Changala, Center for Astrophysics, Harvard & Smithsonian, Cambridge MA, USA

P. Bryan Changala. Vibronic mean-field and perturbation theory for Jahn-Teller and pseudo-Jahn-Teller molecules

doi:10.1080/00268976.2021.1962556. Article: e1962556. [2]

Molecular Physics Early Career Researcher Prize Winner 2021

Tarak Karmaker, Institute of Computational Sciences, Faculty of Informatics, Universit della Svizzera italiana, Lugano, Switzerland

Tarak Karmaker, Michele Invernizzi, Valerio Rizzi, and Michele Parrinello. Collective variables for the study of crystallisation. doi:10.1080/00268976.2021.1893848. Article: e1893848 [3]

The prize-winning papers will be free to access online until the end of December 2023.

Profiles of the Early Career Research Prize winners will also appear in forthcoming issues of Molecular Physics.

We congratulate all authors on their valuable contributions to the journal in 2021.

Molecular Physics will continue to support emerging, early career authors in all its scientific areas of interest. We hope that these prizes will continue to highlight and inspire high-quality work from the next generation of researchers.

For information on eligibility for nomination for an early career researcher for next year's prize and to read prize-winning papers which have been published in Molecular Physics, please visit:

Article collection: Longuet-Higgins Early Career Researcher Prize (tandfonline.com)