Molecular spectroscopy in the data age

June 16, 2020

For the longest time, data about molecules was hidden in analogue media and therefore widely inaccessible for researchers. Now, molecular physicists at the Fritz Haber Institute have created a database to make spectroscopic information on molecules available at the touch of a button.

The Diatomic Molecular Spectroscopy Database

Even though we live in a world that appears fully digitalized and where any type of knowledge seems to be directly available, this is not necessarily always the case in the world of science. While some scientists have digital access to the resources they need, others do not. For the longest time molecular physicists were among the latter group – until now.

There is an enormous amount of data around about molecules. After all, each one of them in the universe has a particular fingerprint that uniquely characterizes it, and which can be identified through molecular spectroscopy. Since the early times of quantum theory in the 1920s, spectra of diatomic molecules have been recorded and analyzed. Unfortunately, though, the information gathered in the last hundred years cannot be digitally retrieved, because it is mainly stored in either analogue media or hidden behind paywalls of scientific journals. “That’s a sad state in the big data age,” says Jesús Pérez Ríos, Group Leader at the Molecular Physics Department at the Fritz Haber Institute. While big data has rightly been met with considerable criticism regarding privacy and the ethics of using personal data for economic gain, there is a different side to it when it comes to research. “Both science and technology thrive on shared data,” explains Pérez Ríos, “it is the cornerstone of scientific development nowadays. This has nothing to do with economic exploitation, but everything with scientific democratization. Every researcher should have uninhibited access to existing data, that is the fair thing to do scientifically.”

That is why Pérez Ríos together with his team members Stefan Truppe and Xiangyue Liu in the Department of Molecular Physics has developed the first open-access and user-friendly website for the spectroscopic constants of diatomic molecules. The "Diatomic Molecular Spectroscopy Database" contains experimental data derived from Huber and Herzberg’s Molecular Spectra and Molecular Structure (1979), the most significant reference book for molecular spectroscopy. The availability of this data is chiefly important for other scientists, like those in the fields of astrochemistry, chemical physics, and ultracold physics. “Imagine a chemical physicist needing to figure out if a molecule is a good candidate for laser cooling (i.e. slowing down the motion of atoms to cool a substance),” expounds Pérez Ríos. “For this, they need to know the spectroscopic constants of the ground and the first excited electronic state. While in the past the potential unavailability of the analogue data would have slowed down the progress of that experiment, now our website contains everything needed.”

There, the user can look at and play with all available data on molecules. One may for example retrieve the spectroscopic constants of any molecule in a convenient and standardized format. Or calculate the Franck-Condon factors between the ground electronic state and excited one (the only property of a molecule that can be calculated) on the fly. Furthermore, the website is dynamic: users can upload new data. Having the data in a useful format also helps the development of a data-driven approach for molecular spectroscopy, which researchers at the Department of Molecular Physics are currently working on.

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