van Helden, Jean-Pierre

The dataset contains results from application of a mid-infrared frequency comb-based Fourier transform spectrometer to measure high-resolution spectra of plasmas containing hydrogen, nitrogen, and a carbon source in the 2800 – 3400 cm–1 range. The spectrally broadband and high-resolution capabilities of this technique enable quantum-state-resolved spectroscopy of multiple plasma-generated species simultaneously, including CH4, C2H2, C2H6, NH3, and HCN, providing detailed information beyond the limitations of current methods.

Plasma-activated chemical transformations promise the efficient synthesis of salient chemical products. However, the reaction pathways that lead to desirable products are often unknown, and key quantum-state-resolved information regarding the involved molecular species is lacking. Here we use quantum cascade laser dual-comb spectroscopy (QCL-DCS) to probe plasma-activated NH3 generation with rotational and vibrational state resolution, quantifying state-specific number densities via broadband spectral analysis.

This work serves to highlight the difference of the distinct spatial distribution of H2O2 (hydrogen peroxide) in the effluent of the kINPen-sci plasma jet and the COST reference microplasma jet (COST Jet) operated with humidified helium. For this purpose, the density of H2O2 has been measured spatially resolved using cavity-enhanced absorption spectroscopy employing continuous wave cavity ring-down spectroscopy (cw-CRDS) with a tunable mid-infrared laser.

This data set contains the data shown in the corresponding publication in Applied Physics Letters (https://doi.org/10.1063/5.0160303). This publication presents a benchmark of THz absorption spectroscopy against a more established method. Atomic oxygen densities were measured with THz absorption spectroscopy and compared to those obtained from picosecond (ps) two-photon absorption laser induced fluorescence (TALIF) measurements on the same capacitively coupled radio frequency oxygen discharge.

Laser absorption spectroscopy (LAS) was applied to investigate a low pressure DC-pulsed discharge in N2-H2 gas mixtures with addition of CH4 or O2. The discharge was maintained in an industrial-scale, active screen plasma nitrocarburizing (ASPNC) reactor with a steel active screen (AS). Spectroscopic lines of CH4, NH3, HCN, CO and H2O were recorded. The dataset contains the species densities for different gas mixtures.

The data set comprises full cavity ring-down spectra and absorption coefficients obtained from on/off-resonance measurements, in order to determine the spatial distribution of H2O2 in the cold atmospheric pressure plasma jet kINPen-sci. Therefore, the plasma jet was operated with 3 slm Ar and 3000 ppm water, and was equipped with a gas curtain of 5 slm O2. To determine the effective absorption length, the H2O2 absorption was measured in radial direction. These radial fits had a Gaussian-like shape.

This data set contains the data shown in the corresponding publication in Plasma Sources Science and Technology (https://doi.org/10.1088/1361-6595/acb815). This publication presents the first implementation of terahertz (THz) quantum cascade lasers (QCLs) for high-resolution absorption spectroscopy on plasmas. Absolute densities of ground state atomic oxygen were directly obtained by using the fine structure transition at approximately 4.75 THz.

A self-consistent fluid model has been successfully developed and employed to model an electron cyclotron resonance driven hydrogen plasma at low pressure. This model has enabled key insights to be made on the mutual interaction of microwave propagation, power density, plasma generation, and species transport at conditions where the critical plasma density is exceeded. The model has been verified by two experimental methods.

Absolute ground state atomic hydrogen densities were measured, by utilisation of two-photon absorption laser induced fluorescence (TALIF), in a low pressure electron cyclotron resonance plasma as a function of nitrogen admixtures - 0 to 5000 ppm. At nitrogen admixtures of 1500 ppm and higher the spectral distribution of the fluorescence changes from a single Gaussian to a double Gaussian distribution; this is due to a separate, nascent, contribution arising from the photolysis of an ammonia molecule.

The data set comprises full cavity ring-down spectra and absorption coefficients obtained from on-off-resonance measurements, in order to determine the spatial distribution of HO₂ in the cold atmospheric pressure plasma jet kINPen-sci. Therefore, the plasma jet was operated with 3 slm Ar and 3000 ppm water, and was equipped with a gas curtain of 5 slm O₂. To determine the effective absorption length, the HO₂ absorption was measured in radial direction. These radial fits had a Gaussian-like shape.