No abstract

Through the utilization of a generalized computer code that calculates the minimum reactive branching ratio required for a species to display optical gain, a parametric study was performed to ascertain which properties of the electronic potential curves of a heteronuclear diatomic molecule have the greatest effect on the suitability of that molecule as a potential electronic transition laser. The results of this study demonstrate that diatomic systems separate into different classes when the question of the minimum required reactive branching ratio is confronted. This separation of molecular systems was translated through the use of compiled molecular constants into a determination of which vibrational-level distribution class is most favorable for specific heteronuclear diatomic molecules to display optical gain; potential laser candidates were pointed out. In addition, a generalized gain equation for electronic transitions heteronuclear diatomic molecules that takes into account both rotational and vibrati nal partitioning was derived.

By means of fast-discharge circuitry, intense laser emission was observed from the XeF molecule at 351, 353, and 349 nm in a gas mixture of He, Xe, and NF3. The over-all electrical efficiency based on the energy deposited in the gas was 1.2%; the ’’wall-plug’’ efficiency was 0.2%. An output energy of 1 mJ was measured from a laser pulse 40 nsec in duration, yielding a peak power of 25 kW. A simple model is proposed to estimate the laser performance.

Output pulse observations are presented for a helium-diluted CO2 laser pumped by VV (vibration-vibration) energy transfer from vibrationally excited DF produced by the D2–F2 chain reaction. Flash photolysis of the F2 served to initiate the reaction. A 290-cm3 reaction chamber containing a 0.5-atm mixture with mole ratio D2:F2:CO2:He = 0.33:1:8:10 gave a single-pulse output energy of 2.8 J. Relative to the amount of D2 present in the reaction chamber, this corresponds to a chemical efficiency greater than 5%.

Laser action has been observed from the P-branch vibration-rotation bands of the HF molecule from v = 6→5 to v = 1→0 transitions. In addition, the time-resolved spectral behavior of this He-diluted H2–F2 chain reaction chemical laser has been recorded. The HF* lasing molecules were produced by the reaction of a 50-Torr gaseous mixture with mole ratio H2/F2/He=0.5/1/40 initiated by flash photolysis. In contrast to earlier results, strong lasing was found on the v = 6→5 and 5→4 transitions of the HF molecule. Within some of the bands from which lasing was observed, the time sequencing of transitions suggests non-Boltzmann distributions of the rotational states.