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Researchers at the Technion, together with theorists from Canada and the Netherlands, have developed an innovative method for predicting the behavior of a molecule in a molecule-surface collision. The method enables the study of basic reaction mechanisms that form the basis of important industrial processes such as hydrogen and ammonia production.

By Lotem Buchbinder

Prof. Gil Alexandrovich

The encounter between two substances is the heart of chemistry, and its outcome depends on the chemical identity of the two substances and other variables, including the velocity of the molecule and the collision angle. Researchers at the Technion’s Schulich Faculty of Chemistry have developed an innovative method for controlling the rotational state of a molecule before it collides with a surface made of a different substance, in order to characterize these states and measure the molecule’s behavior after the collision.

Dr. Oded Godsi

Under the guidance of Prof. Gil Alexandrovich, Dr. Oded Godsi and research students Gefen Corem and Yossi Alkoby have developed a general method for studying the behavior of molecules in molecule-surface collisions. The research group focused on hydrogen molecules that collide with flat and stepped copper surfaces at the same speed, but in different rotational states. The researchers found that when the surface is stepped, the effect of the molecule’s rotational state on the pattern of return from the surface is greater. The system developed and built at the Technion enables full control of the molecule’s rotational state by means of magnetic fields. This system contains a detector that makes it possible to identify the molecules that return from the surface and measure their rotational orientation in space.

Gefen Corem

In order to provide theoretical backup for the method developed by Prof. Alexandrowicz’s research group, his colleague at the faculty Prof. Tsofar Maniv entered the picture, along with research groups from Canada and the Netherlands. These groups helped analyze the results and develop the theory, in order to provide a theoretical model linking the molecule’s rotational states to the results of the collision.

The method developed represents significant progress in the study of the dynamics of chemical reactions, and Prof. Alexandrowicz plans to expand its use to molecules such as methane and ammonia, which are widely used in industry, and to platinum and iron surfaces. Prof. Alexandrovich estimates that “the development of measurement capabilities, followed by the development of new computation methods, will help the chemical industries in the future. Measurements of basic reaction mechanisms, and an understanding of the factors that influence the outcomes of molecule-surface collisions, are an essential stage in the development of computational models of chemical reactions. In the end, these models will enable control of reaction results by selecting optimal surfaces, thereby increasing the efficiency of various chemical processes.”  

The study was funded by the European Union (ERC grant), the German-Israeli Foundation for Scientific Research and the Natural Sciences and Engineering Research Council of Canada.

Source: https://www.nature.com/articles/ncomms15357