Laser technique enables precise gas temperature measurement in real-world conditions
Researchers have developed a new way to measure gas temperature using laser-induced plasma, achieving high precision without disrupting the original molecular state. The method could improve quality control in chemical manufacturing, combustion diagnostics, and industrial processes where accurate real-time temperature data is critical.
Originaltitel: Coherent N<sub>2</sub><sup>+</sup> emission mediated by coherent Raman scattering for gas-phase thermometry
<p>We report on the generation of coherent emission from femtosecond (fs) laser-induced filaments mediated by ultrabroadband coherent Raman scattering (CRS), and we investigate its application for high-resolution gas-phase thermometry. Broadband 35-fs, 800-nm pump pulses generate the filament through photoionization of the N<sub>2</sub> molecules, while narrowband picosecond (ps) pulses at 400 nm seed the fluorescent plasma medium via generation of an ultrabroadband CRS signal, resulting in a narrowband and highly spatiotemporally coherent emission at 428 nm. This emission satisfies the phase-matching for the crossed pump-probe beams geometry, and its polarization follows the CRS signal polarization. We perform spectroscopy on the coherent N2<sup>+</sup> signal to investigate the rotational energy distribution of the N2<sup>+</sup> ions in the excited B<sup>2</sup>Σ<sub>u</sub><sup>+</sup> electronic state and demonstrate that the ionization mechanism of the N2 molecules preserves the original Boltzmann distribution to within the experimental conditions tested.</p>