Time-Resolved Spectroscopy of a Flash-Initiated H2–F2 Laser

The time-dependent output spectrum of a helium-diluted H2–F2 chain-reaction chemical laser has been observed. Reaction of a 50-Torr mixture with mole ratio H2 : F2 : He = 1 : 1 : 60 was initiated by flash photolysis of the F2. Strong lasing was found from P-branch vibration-rotation transitions of the v = 1 → 0, 2 → 1, 3 → 2, and 4 → 3 bands of HF. Within some bands, the time sequence of transitions suggests non-Boltzmann distributions of rotational states. No lasing from vibrational levels higher than 4 could be detected.