text: Site specific isotope enrichments of NO is measured in the environment to help disentangle microbial sources and sinks in the environment. Different isotopologues of N2O absorb light at different wavelengths. Laser spectroscopy converts these differences as it scans across wavelengths to measure the abundance of N-N-O vs. N-N-O, a distinction that is impossible on other instruments. These measurements have achieved very high precision, down to 0.2 per mille.