Position Summary
Laser-Induced Breakdown Spectroscopy (LIBS) is an analytical technique that determines, under specific conditions, the elemental composition of a material by analysing the light emitted by a plasma generated via a laser pulse. Although widely used in fields such as metallurgy and environmental monitoring, it is proving highly promising for the study of nano-aerosols, a critical challenge in atmospheric pollution and public health. Recent experiments have demonstrated the feasibility of acquiring LIBS spectra from these particles using an aerodynamic lens system that concentrates aerosols within a vacuum chamber, thereby enhancing sensitivity and enabling single-particle analysis. However, this application remains sparsely documented, largely due to the complexity of laser-nanoaerosol interactions and the resulting non-standard plasma. To address these challenges, ongoing theoretical and experimental work aims to adapt existing simulation tools and develop novel models. The proposed internship falls within this scope, with the objective of contributing to the modelling of LIBS spectra by providing experimental data to refine the theoretical models currently under development.
Job Availability
01/02/2027
Contract Duration
5-6 months
Job Description
Context
Laser-Induced Breakdown Spectroscopy (LIBS [1]) is a powerful analytical technique used to determine the multi-elemental composition of a bulk sample. Its operating principle relies on analysing the light emitted by a plasma generated during the irradiation of a sample by a high-energy laser pulse (several GW/cm2). Thanks to a thorough understanding of plasma generation and photon emission mechanisms, LIBS now enables the identification of elemental composition in materials with enhanced reliability. Although research is ongoing to optimise quantitative analyses, LIBS is already widely employed to characterise bulk materials across various fields (metallurgy, environment, cultural heritage, etc.).
LIBS is now emerging as a promising technique for the analysis of sub-micron aerosols, a major challenge in atmospheric pollution, particle dispersion, and public health. Preliminary experiments conducted at NIMBE [2] have demonstrated the feasibility of acquiring LIBS spectra from the interaction between nano-aerosols and a laser pulse [3]. In these experiments, an aerodynamic lens system is used to produce a dense, narrow, and collinear beam of aerosols inside a vacuum chamber. The LIBS technique is then used to acquire a spectrum comprising, inter alia, the atomic and ionic lines of the constituent atoms of the aerosols. This configuration enables:
- enhancing detection sensitivity by limiting atmospheric interference;
- isolating the interaction between a nano-aerosol and the laser pulse, thereby paving the way for single-particle analysis.
Conversely, the application of LIBS to nano-aerosols, particularly under vacuum conditions, remains insufficiently documented [3, 4] from both theoretical and experimental perspectives. The primary challenges include:
- detection sensitivity, constrained by the reduced particle size and the complex dynamics of the generated plasma (plasma out of Local Thermodynamic Equilibrium);
- an as-yet incomplete understanding of laser-nanoaerosol interaction mechanisms.
To overcome these obstacles, two approaches are currently being explored. Experimentally, a novel setup has been developed and must be optimised to improve the signal-to-noise ratio and limit of detection. Theoretically, work is underway to adapt existing tools (simulations, physical models) to vacuum-based laser-nano-aerosol interactions and to develop new models describing plasma dynamics under these specific conditions.
Objectives
During this internship, you will actively contribute to the refinement of the existing experimental setup to enhance its sensitivity and improve the signal-to-noise ratio of the detected signals. To this end, you will carry out:
- the improvement of the optical collection system;
- the optimisation of the laser-nanoparticle interaction: laser focusing, pulse duration, pulse energy, repetition rate;
- the synchronisation of data acquisition relative to the laser, plasma lifetime, etc.
These improvements will enable you to refine the limits of detection for each element, even when embedded within a complex matrix.
To successfully accomplish this work, model nanoparticles (NPs) will be selected. These are precisely defined in terms of size distribution, structure, and composition. It will then be possible to establish a clear correlation between the characteristics of the studied nanoparticles (size, composition) and the LIBS signal: matrix effects, the LIBS response of specific minor chemical elements, and the total or partial vaporisation of the NPs.
More specifically, all experiments conducted aim to understand the influence of these characteristic nanoparticle parameters on the evolution of the LIBS signal. This experimental work is essential yet insufficient; understanding the mechanisms of laser-nanoparticle interaction and plasma dynamics under vacuum requires the development and validation of new theoretical models. Comparing experimental spectra with simulated ones will enable their validation, facilitating information extraction and model refinement. These models are developed at CORIA (see Envisaged Collaboration).
Envisaged Collaboration
Arnaud Bultel, Vincent Morel, Aurélien Favre: Reactive Flows [5] research group at CORIA (COmplexe de Recherche Interprofessionnel en Aérothermochimie) located in Saint-Étienne-du-Rouvray. This collaboration will allow for discussions regarding plasma dynamics and the comparison of experimental spectra with simulated data to validate the information obtained and refine the theoretical models developed at CORIA. Depending on the progress of the internship, an introduction to the computational codes developed at CORIA, namely MERLIN [6] and ECHREM [7], may also be possible.
Skills Developed
During this internship, you will develop the following competencies:
- Physicochemical characterisation of nanoparticles;
- Optics: lasers, spectrometers, and atomic spectroscopy;
- Participation in cutting-edge laser spectroscopy experiments;
- Critical analysis of experimental and theoretical data.
Impact of the Internship
Your work will directly contribute to the improvement of theoretical models for the LIBS analysis of nano-aerosols. The experimental validation of the developed tools will pave the way for applications in environmental science, public health, and industrial safety.
Potential PhD Opportunity
Yes, subject to funding availability.
Useful Links
References
[2] https://iramis.cea.fr/nimbe/.
[3] C. Alvarez-Llamas et al., “Online elemental characterization of collimated nanoaerosols by laser-induced breakdown spectroscopy of isolated particles,” Spectrochim. Acta B, vol. 225, p. 107122, 2025.
[4] P. Purohit et al., “Subfemtogram Simultaneous Elemental Detection in Multicomponent Nanomatrices Using Laser-Induced Plasma Emission Spectroscopy within Atmospheric Pressure Optical Traps,” Anal. Chem., vol. 91.11, p. 7444, 2019.
[5] https://www.coria.fr/departement/ecoulements-reactifs/.
[6] A. Favre et al., “MERLIN, an adaptative LTE radiative transfer model for any mixture : Validation on Eurofer97 in argon atmosphere,” J. Quant. Spectrosc. Radiat. Transf., vol. 330, p. 109222, 2025.
[7] V. Morel et al., “Dynamics of a femtosecond/picosecond laser-induced aluminum plasma out of thermodynamic equilibrium in a nitrogen background gas,” Spectrochim. Acta B, vols. 103-104, p. 112, 2015.
Workplace Location
Site
CEA Saclay, (91) Essonne, France
Candidate Criteria
Candidate Profile
Final-year engineering school student or Master 2 student in physical chemistry, optics, or plasma physics. Knowledge of atomic physics is desirable, alongside proficiency in at least one of the following domains: physical chemistry, optics, or plasma physics. A lack of prior knowledge in some of these specific areas can be supplemented during the internship and is not exclusionary.
Other Required Skills
- Computer languages and software: programming proficiency (Python, C, or equivalent).
Languages
English (Intermediate)