In the realm of energy research, understanding molecular fragmentation processes can have significant implications for various applications, including plasma processing and fusion energy. A team of researchers from the Tata Institute of Fundamental Research in Mumbai, India, led by Akash Srivastav, has delved into the fragmentation of carbon dioxide (CO2) molecules when they collide with highly charged argon ions. Their findings, published in the Journal of Physical Chemistry A, shed light on the intricate dynamics of these collisions and the resulting molecular break-up processes.
The researchers investigated the fragmentation of CO2 molecules that have lost three electrons (CO23+), focusing on the specific break-up channel that produces three positively charged particles: O+, C+, and O+. This fragmentation occurs when CO2 molecules collide with slow-moving, highly charged argon ions (Arq+, where q ranges from 4 to 16). By using a method called the native-frames method, the team was able to distinguish between two types of break-up processes: sequential and concerted.
Sequential break-up involves the molecule first breaking into two parts, which then further fragment into the final products. Concerted break-up, on the other hand, is a more simultaneous process where the molecule breaks into all final products at once. The researchers found that the kinetic energy released in these processes, known as kinetic energy release (KER) distributions, varied depending on the type of break-up and the charge of the projectile ion.
For sequential break-up, the KER distributions remained relatively unchanged across the range of projectile charges studied. However, for concerted break-up, the KER distributions showed pronounced but non-systematic variations with projectile charge. Notably, the team observed a low KER feature around 15.5 eV for collisions with Ar4+ and, to a lesser extent, Ar6+. This feature was previously associated with sequential break-up in electron and proton impact but was found to originate predominantly from concerted break-up of specific electronic states of CO23+.
The researchers also examined the branching ratios of the two break-up pathways, which describe the relative likelihood of each process occurring. They found that, with some exceptions, the fraction of concerted break-up decreased with increasing projectile charge, while the fraction of sequential break-up increased. This underscores the importance of considering the detailed electronic structure of the projectile, rather than just its charge, to fully understand the collisional dynamics in slow, highly charged ion collisions.
The practical applications of this research for the energy sector are manifold. In plasma processing, for instance, understanding molecular fragmentation can help optimize processes for etching and deposition in semiconductor manufacturing. In fusion energy, where plasma-wall interactions are a critical concern, insights into molecular break-up can aid in developing materials and strategies to mitigate damage and improve reactor performance. By providing a more comprehensive understanding of collisional dynamics, this research contributes to the ongoing efforts to harness and control plasma for various energy applications.
Source: Srivastav, A.; Srivastav, S.; Bapat, B. Electron Capture Induced Fragmentation of CO23+: Influence of Projectile Charge on Sequential and Concerted Break-up Pathways. Journal of Physical Chemistry A 2023.
This article is based on research available at arXiv.