Theodore A. Jacobs

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.

Shock‐Tube Studies of Sulfur Hexafluoride

Shock‐tube kinetic studies of SF6 dissociation in argon have been made in the temperature range of 1650°–2050°K at pressures from 0.13–30 atm. Rate constants for the initial fragmentation of SF6 have been determined and have been found to be explainable in terms of classical unimolecular reaction kinetics. The analysis of the data in terms of the RRK theory yielded S = 6, λD = 0.25, E0 = 75.92 kcal/mole, and A = 1012.95sec−1 as the best values of the unimolecular parameters. The data did not rule out values of 5 to 7 for S or a factor of 2 range in λD with corresponding variations of about 4 kcal/mole in E0 and a factor of 3 in A. E0 = 75.92 kcal/mole represents the strength of the first S–F bond. Both ir and uv techniques were used to obtain the data.

PRELIMINARY PERFORMANCE OF A cw CHEMICAL LASER

Preliminary performance of a cw chemical laser is presented. Hydrogen is diffused into a supersonic stream containing F atoms. Population inversion is due to the reaction H2+F→ HF(v)+H, ΔH=−31.7 kcal/mole, v=1, 2. An atomic F flow rate of 0.030 moles/sec has produced 475 W of laser power in the 3‐μ region. This represents 12% of the chemical energy involved in the above reaction. Zero power gain is 8%/cm. Spectroscopic observations of laser transitions are included.

Dissociation of Cl2 in Shock Waves

The dissociation of Cl2 in Cl2–Ar mixtures was measured in a shock tube over the temperature range 1700° to 2500°K. Direct absorption spectrophotometry was used to follow the course of the reaction. A rate constant given by k=8.90×1013 exp —48 300/RT cm3/mole‐sec [or,alternatively,k=3.13×1012(57 080/RT)2.087exp−57 080/RT cm3/mole·sec] was found to fit the measured data over the entire temperature range with a most probably error of ±6%. The activation energy determined agreed exactly with that measured by Hiraoka and Hardwick although the over‐all rate constants were a factor of 10 lower than those reported by these investigators. Recombination rate constants, calculated from the measured dissociation rate constants by use of the thermodynamic equilibrium constant, were found to be in good agreement with the theoretical predictions of Benson and Fueno.

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: I. POWER

Abstract : A continuous DF chemical laser radiating at approximately 4 microns is reported. Population inversion is obtained by diffusing D2 into a supersonic free jet containing F atoms. The performance of the DF laser is compared with a similar HF laser previously reported. The ratio of DF to HF laser output power is 0.7 for fixed supersonic jet conditions and the same molar flow of H2 and D2. The efficiency of conversion of chemical energy to laser energy is approximately 12% and 8% for the HF and DF lasers, respectively. (Author)

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.

Initial performance of a CW chemical laser

The performance of a continuous HF chemical laser is presented in this paper. Population inversion was obtained by diffusion of H2 into a supersonic jet containing F atoms [H2+F → HF(v)+H1 ΔH=−31.7 kcal/mole]. A peak power of 630 W was obtained with an F atom flow rate of 0.040 mole/sec, and the efficiency of conversion of chemical energy to laser energy was 12%. The performance of a corresponding DF laser is also given. Major laser output is from 2-1 and 1-0 transitions for both lasers. Radiation is at 2.6 to 2.9μm and 3.6 to 4.0μm for the HF and DF lasers, respectively. The ratio of DF to HF laser power is 0.7 under similar flow conditions.

Shock‐Tube Study of Radiation from S2

Absolute emission intensity measurements of the radiation from sulfur molecules S2 have been obtained in the temperature range from 2300 to 4800°K at six wavelengths spaced between 3132 and 5461 A. The radiation intensities were proportional to the square of the sulfur atom concentration and were independent of the total pressure of the buffer gas, argon. In addition, the band structure was recorded for the wavelength interval 3600–4100 A with an image orthicon camera mounted in a spectrograph. The intensities between 3650 and 5461 A have similar activation energies and are interpreted in terms of the radiative transitions from the B 3Σu− state of molecular sulfur, this state being populated by the mechanism of inverse predissociation. Theoretical calculations of the B 3Σu− bands predicted the band shapes observed with the image orthicon and, together with the measured intensities, provide the electronic f value for the bands. The square of the transition moment [Re(r) / ea0]2 is estimated to have a value...