Researcher Marius Gerlach wins Agnes-Pockels-PhD Award

The 2025 Agnes-Pockets-PhD prize for outstanding research in the field of Physical Chemistry has been awarded to HFML-FELIX researcher Marius Gerlach. In his thesis he studied the interesting, but very difficult to work with molecule fulminic acid (HCNO).

This small molecule with only four atoms has been known since the year 1800, thanks to the work of English chemist Edward Howard. He first prepared salts of fulminic acid by reacting mercury oxide, nitric acid, and ethanol, creating a very explosive substance. That is where the molecule got its name from: the Latin fulminare, meaning “to strike like lightning”. You might also recognize this mercury fulminate salt from a particular scene in the TV-series Breaking Bad, where main character Walter White supposedly uses a similar salt to blow up a drug dealers headquarters.

Through the years, HCNO – which is not explosive by itself – has served as a model molecule, helping chemists to understand a variety of new techniques. ‘More recently, it has also been of interest to scientists because it was detected in space’, Gerlach adds. ‘That makes it even more interesting to study, as it is one of the smallest molecules containing the essential atoms for organic life. It is however also a very unstable molecule which rapidly decomposes at temperatures above 0 degrees Celsius, making it difficult to make and work with in experiments.’

Space interaction in the lab

At this point scientists have identified over 300 molecules in space – HCNO being one of them – using different techniques. Even though most of these molecules are not abundantly present, they do interact. With each other, and with interstellar conditions such as radiation.

But what happens when these interactions take place? What chemical processes occur? ‘I decided to study the interaction between HCNO and two types of radiation that can also be found in space: vacuum ultraviolet and soft X-ray radiation. Without knowing for sure if we could actually make these experiments work.’

Eight hour window

Even when stored at -40 degrees Celsius, HCNO decomposes in the span of eight hours. ‘It really doesn’t want to exist very long. So you need to synthesize the molecule regularly when you do experiments. For these particular tests, we went to synchrotron facilities in Switzerland and France, where they have the equipment and radiation beams we needed. We then did shifts around the clock to use our beamtime as efficient as possible. Because HCNO decomposes quickly, it means you always have to have the next sample ready. So it was a lot of work.’

A lot of work that was worth it in the end though, because – as the award already suggests – they managed to successfully study the interaction between HCNO and the two radiation types.

How they interact

In the experiments, what Gerlach looked at was: does HCNO absorb the photons (light particles) with different wavelengths? And what happens next? ‘We found that when it interacts with VUV light, it mostly forms an unexpected product called HCO+. Which is also an important player in the astrochemical realm, that can set in motion other interesting chemistry, due to its reactivity.’

In interacting with the soft x-ray light, they found that over 90 percent of the time, the molecule dissociates. ‘Now we know, okay, most of the time the molecule will break up and when that happens it mostly forms some smaller fragments, like CH+ and NO+.

Deep dive into molecular effects

The other side of the research was the spectroscopy part. Here they look at the process that is responsible for the formation of these new ionised fragments like HCO+. ‘When HCNO interacts with the photons, an electron is bumped out. This is called photoionization. Losing the electron turns the molecule into a positively charged particle; an ion. The electron that was removed from the molecule by the interaction with a photon is called a photoelectron.’

Now spectroscopy – the study of the absorption and emission of light and other radiation by matter – can be used to look at some very interesting effects in the electronic state of the ion produced by the photoionization: the Renner-Teller-effect and the Auger-Meitner-effect. Behind these effects is a world of astonishing scientific stories worth looking into, but in general you could say these are some very complicated and interesting molecular effects. ‘They are very difficult to understand from a quantum theoretical point of view, so actually seeing this happen in experiments is very important. This does not only tell you something about the electronic structure of the particle you are studying, it also tells you something about whether the theory is correct or not.’

Future research

Of course ideally, you would want to do these measurements for every single one of the 300 plus molecules found in space and with every type of radiation that could interact with them. ‘What I will be doing at HFML-FELIX is investigating molecules that are associated, or somehow related, to HCNO. We want to understand if and how they are formed in space, and if possible use spectroscopy to identify them, forming a so called ‘fingerprint’. This can then be used to compare to measurements done by space telescopes, so we can better determine what molecules can be found out there and how they behave. And perhaps even: how organic life can form when certain interactions occur.’

Research contact: Marius Gerlach