Use of a tunable GaAs injection laser in optoacoustic detection of absorption by hydrogen fluoride molecules

A tunable pulse GaAs injection laser was used in measurements of weak molecular absorption. The frequency was tuned by varying the applied hydrostatic pressure and current. The absorption sensitivity of an optoacoustic detector used in the study was 2.5X10^–12 J cm^–1 so that, when the energy of a laser pulse was 10^–8–10^–6 J, it was possible to record the absorption in gases at the 10^–3–10^–5 cm^–1 level. An experimental study was made of the second absorption harmonic of the HF molecules.