Hydrogen bonds are small but essential forces that play a central role in many processes in nature, including those involved in life. They are also important in chemistry and in the development of new technologies. Despite their importance, many details of how hydrogen bonds form and how protons move between molecules are still not fully understood. This thesis explores these processes by studying molecules at extremely low temperatures, close to absolute zero. The experiments use small droplets of superfluid helium to provide a very gentle and controlled environment for investigating individual molecules. Infrared light is then used to observe how the molecules respond, providing detailed information about their structure and behaviour. The method is used to study several hydrogen-bonded systems. One study examines how a proton is held within a ring-shaped molecule and how its behaviour changes with temperature. Another investigates clusters of phosphoric acid, revealing an unusual way in which the molecules interact that challenges some conventional ideas about acids and bases. Finally, a new spectroscopic technique using two infrared lasers is introduced to distinguish between different forms of the same molecule and follow their interconversion. The studies demonstrate new ways of observing and understanding the fundamental interactions that govern molecular behaviour in these systems.
América Y. Torres-Boy is a doctoral researcher at the Fritz Haber Institute of the Max Planck Society in Berlin, working in molecular physics. Her research focuses on understanding molecular structure, hydrogen bonding, and proton-transfer processes using cryogenic infrared spectroscopy and helium nanodroplet ion spectroscopy. Her work combines mass spectrometry, infrared spectroscopy, and ultracold helium nanodroplets to investigate molecular ions and hydrogen-bonded complexes under highly controlled conditions. Her research has included studies of proton-bound molecular complexes, phosphoric acid clusters, and other chemically relevant ions. She contributed to the development of a new technique that, for the first time, uses two free-electron lasers simultaneously to control the populations of different molecular structures and reveal spectra of isomers that are otherwise hidden. Her academic background includes studies at the Universidad de Guanajuato, and research internships in Germany, The Netherlands and USA.