High-precision spectroscopy on molecular hydrogen and molecular deuterium
Researchers in Amsterdam and Zurich have taken an important step in extremely precise measurements of molecular hydrogen and molecular deuterium - the simplest neutral molecules in the universe. Such precision is critical because such measurements help physicists test whether our current theories about nature are still correct, or whether there are clues to unknown physical phenomena.
Molecular hydrogen consists of two hydrogen atoms bound together. Scientists have been trying for more than a century to determine exactly how much energy is required to break that bond: the so-called dissociation energy. Precisely because the molecule is so simple, theorists can make very precise calculations. Experimental measurements are then the ultimate test. If experiment and theory do not match, it may point to new physics outside current models.
Physicist Charlaine Roth and her colleagues developed an innovative measurement method, Ramsey comb spectroscopy, which can be used to investigate energy levels in molecular hydrogen with unprecedented precision. Using this technique, a crucial first energy step was measured 100 times more precisely than before.
Together with researchers at ETH Zurich, the remaining energy required to completely dissociate the two atoms was then also measured. This ultimately allowed the dissociation energy of molecular hydrogen to be determined five times more accurately than previously possible.
The outcome is striking: the new measurements are in complete agreement with theoretical predictions. This reaffirmed that current physical theories work extremely accurately - but at the same time, the limits of those theories are being tested ever more closely.
The social and scientific impact of this kind of precision research extends beyond fundamental physics alone. Techniques developed for ultra-sharp spectroscopy often later find applications in, for example, quantum technology, advanced sensors and high-precision time measurements. In addition, future, even more precise experiments could potentially reveal anomalies that provide clues about great mysteries in the universe, such as dark matter and dark energy.
Roth: "The results mark the beginning of a new phase in the international race between experiment and theory. Further improvements in measurements will force theorists to hone their calculations again - in the quest for an even deeper understanding of the laws of nature that govern our universe."
Learn more about the dissertation