Laser-induced gratings in oxygen excited via the b 1Σg+(v′ = 0) state

Laser-induced gratings have been generated by exciting transitions in the red system of molecular oxygen. The temporal evolution of the grating reflectivity has been studied at room temperature and atmospheric pressure. Contributions to the grating reflectivity arise from a change in population distribution caused by absorption, from electrostriction, and from a release of absorbed laser energy in form of heat. Adding some water to the oxygen sample strongly increases the grating reflectivity rendering the laser-induced grating method sensitive enough to detect the isotopic molecule 16O18O in its natural abundance.