Spectroscopic diagnostics of laser-supported absorption (LSA) waves produced by a HF laser

Abstract
LSA waves have been generated by a pulsed chemical HF laser beam (2.8 μ, 45 J, 7 μsec) when focused on solid surfaces in air. The emission spectrum is found to contain mainly N+ and O+ lines broadened by the Stark effect and superimposed on a strong continuum. The LSA wavefront travels at an average speed of 0.72 cm/μsec as measured by the time‐of‐flight method. Target species such as atomic Al emit light for 600 μsec after the laser pulse. In contrast with the results from a CO2 laser, however, no forbidden transition of AlI is observed.