R. R. Giedt

Kinetics of Hydrogen Halides in Shock Waves. II. A New Measurement of the Hydrogen Dissociation Rate

Abstract : Decomposition rates for H2, diluted in Ar, were studied behind incident shock waves over the temperature range 2900 to 4700 K. HCl and the infrared emission from this molecule were used in a manner to trace the course of decomposition of the H2.

Kinetics of Decomposition of HF in Shock Waves

The decomposition of HF in HF–Ar and HF–H2–Ar mixtures was studied behind incident shock waves over the temperature range 3800° to 5300°K employing infrared emission techniques. For HF dissociation, a rate k1=1019.053T−1 exp (−134 100/RT) or, alternatively, k1=1022.710×T−2 exp (−134 100/RT) was found to best represent the experimental data; the exchange rate for H+HF was found to be k2=1013 exp (−35 000/RT); the recombination rate for H2 was best represented by k−3=1018.30T−1 (all rates are in cubic centimeter—mole units). Rates derived for H–F recombination were found to be in good numerical agreement with the theory of Benson and Fueno.

COMPARISON OF HF AND DF CONTINUOUS CHEMICAL LASERS: II. SPECTROSCOPY

Continuous laser action has been observed on several HF and DF vibrational‐rotational transitions. The HF lases between 2.6 and 2.9μ and DF lases between 3.6 and 4.1μ. The lines are identified and the relative intensities are shown.

Kinetics of Hydrogen Halides in Shock Waves: HCl and DCl

Decomposition rates of HCl and DCl, diluted in an Ar bath, were studied behind incident shock waves over the temperature range 2800° to 4600°K, by application of infrared emission techniques. Within a factor of 2, the dissociation rate constants (cubic centimeters·moles·second units) were found to be as follows. HCl: k1=1021.83T−2 exp (−102 170/RT); DCl: k1=1021.90T−2 exp (−103 200/RT). Evidence is presented to show that a superior match is achieved between experimental and computed time derivatives for HCl and DCl when an activation energy of about 70 kcal is taken for the dissociation step; in this case, a k1=1012.82× exp (−70 000/RT) is found for HCl and DCl.

Kinetics of Hydrogen Halides in Shock Waves. IV. HBr

Shock‐tube studies were made of the thermal dissociation rate of HBr in Ar over the 2100°–4200°K temperature range, using ir emission and uv absorption techniques. It was necessary to invoke a low activation energy (compared to bond energy) in order to explain the HBr dissociation data. The rate constant found for HBr dissociation by Ar was 1012.19 exp(− 50 000/RT cc/mole·sec. It was also found that HBr is about 15 times more efficient than Ar as a collision partner in dissociating HBr.

Reverse wave suppression in unstable ring resonator

The effectiveness of a reverse wave suppressor (RWS) mirror in an unstable ring resonator has been investigated theoretically and experimentally for the case of an inhomogeneously broadened gain medium. The theory indicates that the RWS mirror is effective when (δ/Δνh)2 ≪ 1, where Δνh is the characteristic homogeneous linewidth of the gain medium and δ = Δu(ν0/c) is a measure of the separation between competing forward and reverse waves. Unstable linear ring resonator experiments were conducted using a continuous wave HF laser. Successful suppression of the reverse wave was achieved. In these tests the ratio of forward to reverse power had an average value of 41. An unstable annular ring resonator was investigated using a pulsed CO2 laser. Reverse wave suppression was achieved when the resonator and RWS mirror were in good alignment. Suppression effectiveness and beam quality were degraded when the RWS mirror was tilted.

Kinetics of Hydrogen Halides in Shock Waves. III. The Reactions Cl + HCl→Cl2 + H and Cl + Cl2→3Cl

The decomposition of HCl via the chlorine exchange reaction Cl + HCl⇆Cl2 + H was studied in the shock tube by monitoring the infrared emission from the fundamental band of HCl. Mixtures of 0.2% HCl, 5% Cl2 (balance Ar) and 2% HCl, 5% Cl2 (balance Ar) were employed. Over the 3500°–5200°K temperature range of the experiments, the added Cl2 dissociated rapidly behind the shock waves; the HCl reaction mechanism thus proceeded in a large excess of Cl atoms and was dominated by the chlorine exchange reaction. We found the rate constant for the chlorine exchange reaction to be consistent with the low‐temperature value of Klein and Wolfsberg. The study also yielded the efficiency of Cl atoms in decomposing Cl2. Compared to Ar, Cl was found to be 10 times more efficient.

Variable-aperture calorimeter for an unstable resonator.

A new technique for measuring the output power from a cw edge-coupled unstable resonator has been developed and applied to a cw DF laser. An internal-cavity calorimeter was used that permits measurement of output power with a variable rectangular mode geometry while containing the radiation inside the resonator. The variable aperture calorimeter absorbing scraper (VACAS) device consists of an absorbing copper plate calorimeter assembly, which replaces the 45 degrees output coupling mirror of a conventional edge-coupled unstable cavity. A rectangular hole in the plate of variable width w and height h defines a rectangular mode of variable width Mw and height Mh within the geometric optics approximation, where M is the magnification. Two important applications of VACAS are (1) the determination of the optimum mode geometry for a cw diffusion-type chemical laser where there is significant variation in gain across the unstable resonator mode and (2) the determination of the power tradeoff between mode width and the number of folds in a folded unstable resonator configuration.