The convertible energy of molecules

Text: Sven Titz

How do gas molecules change when they collide on metal surfaces? This is the question American chemist, Alec Wodtke, a world leader in energy research, will address in Göttingen. A highly-decorated scientist, he observes how electrically neutral particles oscillate or gyrate and integrates these results in catalysis research.

Alec Wodtke strides through a lab in the Institute of Physical Chemistry at the University of Göttingen, where his young assistants are busy working. He points to a shiny piece of silvery equipment that looks like part of a ship’s engine. “That’s going to be a vacuum chamber,” says the American chemist. Wodtke has been establishing two working groups at the university and the Max Planck Institute for Biophysical Chemistry since April 2010, getting instruments installed and preparing projects. Experiments will start very soon.

In his research, Wodtke uses lasers, gas molecules and a surface made of gold, all installed in a high vacuum. He wants to discover how chemical reactions take place on surfaces. He particularly likes working with nitric oxide, using laser beams to make it ‘talk’. Targeted energy from a laser beam makes the molecule vibrate. It then pulsates like a spring or spins around itself like a top at breakneck speed. During the experiment the molecule is steered onto a gold surface and observed. The vibrations have a major impact on the way chemical and energetic changes in the molecule take place when it makes contact with the surface.

Testing chemical theories

Chemists always used to rely on the Born-Oppenheimer approximation when examining these processes, according to Wodtke. This is a quantum mechanical description of the molecular state which views atoms as static objects. In reality they are not. A few years ago, Wodtke and other researchers pointed out that the approximation breaks down, particularly when molecules collide on metal surfaces. This sets off electron transfer-like reactions – the type of energy alternating between chemical energy, electric energy and thermal energy.

For groundbreaking research of this kind the chemist received the National Science Foundation’s Presidential Young Investigator Award and the Humboldt Research Award. His findings could help to understand processes similar to those that allow us to convert sunlight into the sort of energy people can use, and to construct chemical sensors. The development of sensors for trace gases like hydrogen, for example, is based on this field of research.

Alec Wodtke and his team want to utilise modern methods like laser spectroscopy to evaluate their new experiments in Göttingen. The chemist hopes to derive the universal rules that steer these transfer processes. This kind of fundamental research may, one day, obviate the necessity for experimentation. For example, chemists are constantly searching for new catalytic substances, which speed up the desired chemical reactions. They used to go about it by trial and error. But times have changed. “If they apply the knowledge we gain from our research, theoreticians may be able to predict chemical reactions they didn’t know about before,” he explains.

From Salt Lake City to Göttingen

When he first started studying, no-one would have guessed that the American student would become an eminent chemist. Wodtke was interested in anthropology and learned some Hebrew. But then he caught the bug – in lectures on physical chemistry. “I realised that you could use it to tackle lots of different research issues,” he explains. He first came to Germany as a postdoc in 1986, working at what was then the Max Planck Institute of Fluid Dynamics in Göttingen.

Even at that time, the American considered staying in Germany permanently. But he decided to accept a position at the University of California in Santa Barbara, where he later became a full professor. While in California, IBM scientist, Daniel Auerbach, introduced him to surface science research. He also gained some commercial experience with a company conducting genetic research. And now he has arrived back in Germany after all: The award of a Humboldt Professorship and the offers made by the university and the Max Planck Institute for Biophysical Chemistry in Göttingen convinced him that his future was in the historic university town in Germany. Wodtke thinks his job and all the opportunities it offers are ‘super’, as is the town itself. Göttingen is the location of the planned International Centre for Advanced Studies of Energy Conversion, where Wodtke will be a key player. He is also building up a partnership with Chinese researchers. But, most of all, the chemist enjoys working together with the excellent colleagues at the university and the Max Planck Institute. And he welcomes the opportunity to teach, especially as he originally toyed with the idea of becoming a teacher. “It’s always exciting working with young people – and hopefully it helps keep you young.”