Scientists have cracked the code on how organic molecules called polycyclic aromatic hydrocarbons (PAHs) can survive the harsh environment of space. In a groundbreaking experiment, researchers discovered that small PAHs use a process called recurrent fluorescence to shed excess vibrational energy, allowing them to evade destruction.
These tiny molecules, which form in dying stars and are ejected into interstellar clouds, were previously thought to be too unstable to withstand the intense ultraviolet radiation and molecular collisions they encounter. However, by studying the behavior of indene, a specific type of PAH found in space, researchers found that it can use recurrent fluorescence to stabilize itself.
The process involves a vibrationally excited molecule gaining energy and then emitting a photon that takes away much of its vibrational energy. This process is faster than traditional cooling methods and allows small PAHs to survive where others would be torn apart.
According to Ilsa Cooke, an astrochemist at the University of British Columbia, this discovery provides critical insights into the survival of small PAHs in interstellar space. The findings also have implications for our understanding of how life’s building blocks are dispersed throughout the cosmos.
The research team used a sophisticated laboratory experiment to study indene, which is thought to be equally abundant in space as another type of ionized PAH called indenyl. By analyzing the behavior of these molecules, researchers were able to develop a new model that takes into account recurrent fluorescence and its role in stabilizing small PAHs.
This breakthrough has significant implications for our understanding of the interstellar lifecycle of PAHs and the possibility of life existing elsewhere in the universe. As Cooke notes, “The next step is for astrochemists to establish the best way to incorporate these findings into their models to better probe the interstellar lifecycle of PAHs.”
Source: https://physics.aps.org/articles/v18/115