The group conducts basic and applied research in optical measurement science to enable the accurate and precise characterization of light-matter interactions. Measurands include amount of substance, isotopic composition, transition moments and frequencies, spectroscopic line shape parameters, scattering and absorption by particles, acoustics and ultrasound and thermophysical quantities such as pressure and temperature. The group develops measurement standards, methods and tools to advance measurement capabilities in areas of national and industrial need, such as characterization of material composition through quantitative chemical sensing, laser spectroscopy, hybrid photonics/mechanical methods and mass spectrometry. The group disseminates spectroscopic and optical reference data for the quantitative analysis and sensing of a wide variety of systems, such as those related to energy transformation, manufacturing, and environmental assessment, remote sensing, environmental radiative transfer and emissions monitoring; develops experimental methods, models, and standards pertaining to sensing applications, and analytic services; interacts with international standards organizations and other National Metrology Institutes to provide comparability among international standards to assure the competitiveness of U.S. industry; and provides advice and measurement traceability to other government agencies (federal and state), scientific organizations, and American industry.