Abstract: A method for spectroscopically detecting a chemical in a gas sample includes illuminating the gas sample with ultraviolet light and photolyzing a first chemical in the gas sample to generate a photolyzed gas sample and spectroscopically detecting a second chemical in the photolyzed gas sample. The second chemical has an optical absorption range within a respective optical absorption range of the first chemical.

Abstract: A method for spectroscopically detecting a chemical in a gas sample includes illuminating the gas sample with ultraviolet light and photolyzing a first chemical in the gas sample to generate a photolyzed gas sample and spectroscopically detecting a second chemical in the photolyzed gas sample. The second chemical has an optical absorption range within a respective optical absorption range of the first chemical.

Abstract: Methods and systems are provided for a vehicle. In one example, a method may include acquiring measurements from at least one exhaust emission sensor of the vehicle, the exhaust emission sensor positioned to measure one of NOx, NH3, and O2 levels in exhaust gas of the vehicle. The measurements may be input into a machine learning model trained to output a predicted real-time amount of at least one exhaust gas constituent in the exhaust gas and operations of an emissions aftertreatment system may be assessed and adjusted based on the predicted real-time amount of the at least one exhaust gas constituent.

Abstract: Methods and systems are provided for a particulate matter sensor. In one example, the particulate matter sensor may include a light source, a waveguide aligned with the light source to receive incident light from the light source, and a photodetector positioned to receive light the incident light from the waveguide. The incident light may be reflected off a reflective surface of the waveguide more than one time to generate a plurality of evanescent waves. The plurality of evanescent waves may interact with particulate matter in exhaust gas, causing the incident light to be attenuated.