Our International Teams aims to bring together experts from different fields (comets and star-forming regions) and with different skills (observations, laboratory, modelling) to discuss the latest results on nuclear spin temperatures in different astronomical environments.
The relative abundance of different spin configurations in multi-hydrogenated species (e.g., H2O, H2, H2CO, NH3) is temperature dependent, and once molecules are formed, strong selection rules prevent the molecules from changing their spin state via radiative or collisional processes. Thus, distinct spin ratios found in various astrochemical environments, including the Interstellar Medium (ISM), proto-planetary disks, and comets, have long been employed as cosmogonic thermometers to determine molecular formation temperatures.
In recent years, the amount of observational data on nuclear spin ratios has grown rapidly, also thanks to increasing instruments sensitivity, and improved statistics and modelling. As a result, a debate about the reliability of these values as cosmogonic thermometers has started. In fact, observed discrepancy in some datasets shows that the nuclear-spin conversion may be possible in some cases, for example through gas-phase reaction in the coma of comets or ice desorption and recondensation in the ISM and proto-planetary disks, as demonstrated through recent ad-hoc laboratory experiments.
We thus have built a working group with the following main objectives:
- Complement the existing spin temperature data on comets and planet-forming regions with the most recent outcomes, especially considering recent JWST observations;
- Update our understanding of spin temperatures considering the latest experimental results and models;
- Understand how to interpret the different results in the context of planet formation.
Header image was AI-generated using Gemini (2025) and then edited for use on this site.