Theoretical study of a high-energy pulsed H₂/F₂ chain first vibrational overtone HF chemical laser

We have theoretically investigated the output performance of a pulsed discharge initiated H₂/F₂ chain first vibrational overtone HF chemical laser. The model used included rotational relaxation processes and simulated simultaneously both fundamental and overtone oscillations since the undesirable fundamental lasing cannot completely be suppressed during the experimental overtone oscillation. In the H₂/F₂ chain reaction system, which can produce the highly vibrationally excited HF(v) molecules up to vibrational level v=6, higher overtone output energy can be expected due to the increased vibrational overtone P branches, the increased transition probability of the first overtone transitions at the higher vibrational levels, and to the relative longer gain duration of a few tens microseconds. The overtone output energy of 2.73 J/l is obtainable from the laser gas mixture of F₂/H₂/He=10/4/786 (Torr). Adding He diluent gas can effectively suppress the undesirable fundamental lasing by pressure broadening; the overtone output energy is much less sensitive to this effect. The overtone output energy is found to be dependent on the residual reflectivity of the resonator mirrors over the fundamental lasing band.