Quantitative spectroscopy is a key enabling technology in modern measurement science, enabling precise determination of chemical composition, temperature, pressure, velocity and other physical quantities through light-matter interaction across the ultraviolet, visible, infrared and terahertz spectral regions. Emission, absorption and scattering spectroscopic methods have become indispensable in industrial process control, energy systems, environmental monitoring, biomedicine, agriculture, security, and extreme environments. Recent advances in laser sources, optoelectronic devices, integrated photonics, and quantum technologies are redefining how spectroscopic measurements are conceived, implemented and applied. These innovations reshape the methodological landscape of spectroscopy as they enable new measurement paradigms, broaden accessible spectral ranges, enhance sensitivity and speed, and unlock applications that were previously impractical. The convergence of these technologies creates unprecedented opportunities for the community to jointly explore novel spectroscopic methods, their metrological foundations, and their transformative potential across disciplines.

This Special Session brings together researchers from metrology institutes, universities and industry to present the latest developments in quantitative spectroscopic methods and applications. The session covers fundamental spectroscopic principles, advanced light sources and detection techniques, spectral data processing and uncertainty analysis, and emerging applications. By fostering interdisciplinary exchange, this Special Session seeks to advance quantitative spectroscopy as a reliable, traceable measurement technology.