Taking quantum control over the building blocks of life

Life (as we know it) is based on carbon. Despite its ubiquity, this important element still holds many secrets, on Earth and in the heavens above. For example, astrophysicists such as Daniel Wolf Savin of Columbia, who study interstellar clouds, want to understand how the chemicals, including carbon, that swirl in these fuzzy accumulations of gas and dust shape the stars and planets scattered throughout our universe and give rise to organic life.

These interstellar clouds are extremely cold and difficult to simulate in a lab, but Columbia has experts in ultra-cold science. During a Physics Department retreat several years ago at Columbia’s Nevis Laboratory, astrophysicist Savin met quantum physicist Sebastian Will. Will’s lab specializes in cooling atoms and molecules to the extreme using lasers. Laser cooling techniques have advanced rapidly in recent years, but physicists’ typical choices for atoms and molecules are uncommon in everyday life. Savin wanted to know: could you cool? carbon molecules?

The answer, at least theoretically, is yes, according to a study recently published by physics student Niccolò Bigagli, Savin and Will in Physical Assessment A†

The starting point for laser cooling an atom or molecule is to understand how it absorbs and radiates light; that process reduces the kinetic energy of the atom or molecule, eventually causing it to cool and almost come to a stop. The required spectroscopic data is challenging to obtain and often requires expensive laboratory equipment, but fortunately data for carbon molecules already existed in the ExoMol database, an open-source University College London source of molecular spectroscopy data that astrophysicists use to study the atmospheres of exoplanets.

Bigagli dug into ExoMol’s data and developed a scheme that should be able to use lasers to cool carbon molecules to extremes cold temperatures— more accurately replicate those conditions within interstellar clouds than was previously possible in the lab, Savin noted. These cold carbon molecules can then be trapped with so-called optical tweezers for highly accurate spectroscopy of their fundamental properties or for reaction experiments to determine their quantum chemistryas indicated by Will.

“Carbon molecules are absolutely essential building blocks for so many other molecules — it’s incredible to think about the possibilities of what we could create with this new laser cooling scheme,” Bigagli said. Combining carbon with . can do that hydrogen atoms to study an important class of molecules called hydrocarbons.

That carbon molecules, which are in some ways quite different from molecules that have hitherto been laser-cooled in labs, are amenable to the technique also raises the possibility that there may be more options on the table than previously realized. “Carbon molecules can be the bridge between the somewhat esoteric” molecules and those studying chemists with more real-life applications,” said Bigagli. The team is currently analyzing additional data to identify other interesting molecules that could potentially be laser cooled, as well as thinking about what they could add to cooled carbon.

Only real experiments will show how successful the carbon cooling scheme will be, Will said, and he hopes his lab can build the necessary laser setups soon. “We’ve shown that this will basically work with state-of-the-art technology — we just need the resources to put it together,” he said.