These helium droplets, being superfluid, have special properties that differentiate them from regular fluids. Their high thermal conductivity helps maintain the droplets and embedded molecules at nearly absolute zero (0 Kelvin). They are also transparent across a wide spectral range, from UV to far infrared, and show minimal interaction with the embedded molecules.
These qualities were essential for the experiment's success, as they enabled the team to study the interaction between two H2S molecules without interference from other molecules or thermal energy. This led to high-resolution infrared spectra that revealed not only the vibrational movements of the H2S dimer but also its rotations and tunneling splittings.
Foundation for a Better Understanding of Hydrogen Bonding
The experimental findings were further supported by theoretical calculations, enabling detailed characterization of the energy splitting of H2S molecules in both their ground and excited states. When compared to water, it was observed that H2S molecules exhibit a more flexible bonding in the ground state. However, upon excitation of one of the H2S molecules, the hydrogen bonding closely resembles that found in water.
Additionally, the researchers were able to re-evaluate and reassign vibrational signals previously published by other chemists, providing a valuable benchmark for advanced computational methods. These methods, used to predict interactions between different molecules, must be validated by experimental data to confirm their accuracy.
Studying the bonding behavior between small molecules like water and H2S significantly advances the understanding of fundamental chemistry, allowing for the refinement of theoretical models and aiding in the analysis of more complex chemical systems.
Journal Reference:
Jäger, S. et. al. (2024) On the nature of hydrogen bonding in the H2S dimer. Nature Communications. doi.org/10.1038/s41467-024-53444-6