Scholar Energy - Kasidapa Polprasarn
In the daily life of a PhD candidate in plasma physics
PhD candidate at the Laboratory of Plasma Physics at École Polytechnique, Kasidapa Polprasarn reflects here on her academic journey and on the way she conducts her doctoral research entitled “In-situ Raman spectroscopy of energy exchanges between cold plasmas and liquid interfaces.”
Making energy exchanges visible through Raman spectroscopy
At the heart of her research lies an invisible frontier: the extremely thin region where a plasma comes into contact with a liquid. At this interface, only a few micrometers thick, intense energy transfers and rapid chemical reactions take place. Yet everything occurs at the molecular scale, making these phenomena particularly difficult to observe.
To make the invisible observable, Kasidapa relies on in-situ Raman spectroscopy, an optical technique based on the use of a laser. This method makes it possible to monitor molecular vibrations in real time. Each molecule scatters light in its own specific way, producing a spectral signature comparable to a fingerprint. By carefully analyzing these signatures, it becomes possible to detect variations in concentration, temperature, or chemical environment.
Observing as close as possible to the surface
Over the course of her PhD, she has refined her experimental setup in order to observe as close as possible to the liquid surface, reducing the detection volume to precisely isolate the interaction zone between the plasma and the liquid. By using nitrate as a probe molecule, she demonstrated that the vibrational profile narrows near the surface and evolves under plasma treatment. Under certain conditions, the signal broadens, likely due to plasma-induced heating. In other cases, the observed changes suggest the presence of chemical reactions specific to the interface.
These results shed new light on plasma–liquid interactions, a field of research with significant implications for environmental technologies, sustainable chemistry, and energy applications. By combining advanced optical diagnostics with rigorous experimental work, her research contributes to a better understanding of how energy is transferred and transformed at the molecular scale.
Fundamental research connected to the energy transition
Beyond its fundamental interest, this research topic is fully aligned with the challenges of the energy transition. Cold plasmas represent a promising pathway to activate chemical reactions at room temperature by injecting energy selectively into electrons rather than in the form of bulk heating. This approach opens the way to more energy-efficient processes for water treatment, pollution remediation, CO₂ valorization, and the production of molecules of energy interest. By gaining a detailed understanding of how energy is transferred and dissipated at the plasma–liquid interface, this work helps improve the efficiency of these emerging technologies and reduce their energy cost, a key issue in building industrial systems compatible with a low-carbon economy.
Her PhD is supported by the Fondation de l’École polytechnique, the Franco-Thai Scholarship Program of Campus France, the Embassy of France in Thailand, and the interdisciplinary center Energy4Climate (E4C).