What are we doing?
The research team of COMB.AT is looking at formally dipole-forbidden transitions that have not yet been excited by lasers in two different substances: carbon-monosulfide (CS) molecules and the 229Th nucleus.
Quantum transitions are changes in the quantum state of a system, such as an atom, molecule, or subatomic particle. These transitions occur when the system absorbs or emits energy, typically in the form of electromagnetic radiation (e.g., photons). Quantum transitions are fundamental to many physical phenomena and underpin various technologies.
For example, they are the basis of spectroscopy, a technique used to study the structure and composition of matter by analyzing the spectrum of absorbed or emitted radiation. Different elements and molecules have unique sets of energy levels, resulting in characteristic spectra. This allows scientists to identify substances and study their properties.
At COMB.AT, five research groups are trying to improve current precision spectroscopy schemes in molecular and nuclear spectroscopy. To do this, we are using light with special properties, in particular light carrying orbital angular momentum (OAM).
Orbital angular momentum refers to a property of these light waves where the phase of the wavefront twists in a helical or spiral manner as it propagates. This twisting results in a structured beam that carries quantized angular momentum in addition to the intrinsic spin angular momentum.
In atomic and molecular physics, transitions between energy levels are governed by selection rules that dictate whether a transition is allowed or forbidden based on certain criteria. We aim to increase the sensitivity of measurements by coupling light with OAM to transitions that are electric-dipole forbidden but magnetic-dipole and electric-quadrupole allowed.
Looking at quantum transitions in molecules or in subatomic particles is often done in isolated groups since you need different mathematical approaches, experimental setups, and knowledge to specialize in one of the two areas. The COMB.AT program allows us to bridge molecular and nuclear spectroscopy, sharing common concepts, methods, and technologies. Our experts target precision measurements on two very different systems: a vacuum ultraviolet nuclear transition in the 229Th nucleus and the first overtone transition in carbon monosulfide as a model molecule for heteronuclear diatomic molecules.