R. Pearson

Electron beam and flashlamp initiation of a pulsed hydrogen fluoride chemical laser

Abstract Laser action was achieved in mixtures of N 2 F 4 -H 2 , N 2 F 4 -B 2 H 6 , and NF 3 -H 2 at a pressure range of 10–250 torr using a 1.4-MeV. 50-nsec pulsed beam of electrons to initiate the chemical reaction volumetrically. The laser emission, in the region 2.7 μ, is attributed to HF, a combustion product. Techniques and results are compared with flashlamp-initiated lasing of the same materials.

Nonradiative intramolecular deactivation of Tb3+ fluorescence in a vapor phase terbium(III) complex

Abstract For the first time, fluorescence lifetime studies are reported for a trivalent rare-earth gas: specifically, for the 5 D 4 state of Tb 3+ in the vapor phase chelate 2,2,6,6-tetramethyl-3,5-heptanedione. Measurements of the fluorescence decay as a function of temperature and pressure demonstrate that intermolecular collisional deactivation is unimportant and that nonradiative deactivation by intramolecular processes dominates the fluorescence lifetime at temperatures of 230–300°C. The rate for the latter processes is well described by an Arrhenius equation and suggests that the Tb 3+ relaxation occurs via transfer to low-lying excited states of the chelate.

Relative performance of a variety of NF 3+ hydrogen-donor transverse discharge HF chemical lasers systems

The performance of 18 NF 3 + hydrogen-donor reactant systems has been determined in a pin-discharge HF chemical laser. Laser energy, laser pulse shape, and the time delay between initiation and lasing were measured in experiments with all 18 reactant systems; lasing lines were measured in 9 systems. It was found that, in general, saturated aliphatic hydrocarbons produced the most laser energy, other hydrocarbons produced less laser energy, and inorganic hydrides produced the least laser energy. Rates of hydrogen abstraction by fluorine atoms have been determined from calculations based on pulse-shape data for the hydrogen compounds used in this study. Ten of these rates have not previously been reported.

Infrared laser single photon absorption reaction chemistry in the solid state. I. The system SiH4–UF6 a)

The reaction between SiH4 and UF6 under thermal gas phase and photon initiated conditions in cryogenic matrices has been investigated. The gas phase thermal reaction begins at 130–140° C producing HF, SiH3F, and a solid uranium fluoride product. When the UF6 is matrix isolated within SiH4 at 12 K and exposed to low power infrared radiation of 25 mW cm−2 using laser emissions resonant with the ν3 band of UF6, a reaction also occurs. This reaction produces SiH3F, UF5, and UF4 as products. The same reaction is also catalyzed using a broad band incoherent source with a photon flux density of 10 μW cm−2. The activation energy for the photoreaction (1.8 kcal mol−1) is considerably lower than the thermal activation barrier for the gas phase reaction. These experiments are part of the bases for uncovering a process of photochemistry of reactants in fixed relative configurations–single photon absorption reaction chemistry in the solid state (SPARCSS). This process is a manifestation of a previously unrecognized, g...

Pressure dependency of the NF 3 -H 2 transverse-discharge pulse-initiated HF chemical laser

The pressure dependency of the performance of the NF 3 -H 2 chemical-laser system has been evaluated. The laser energies at various chemical compositions and initiation discharge energies are presented as functions of Pressure. Overall efficiency, laser pulsewidth, and effects of additive gases are also presented. For all compositions the laser energy maximized at a pressure P_{\max} which was observed to be dependent on the pulsewidth of the initiation discharge. At pressures below P_{\max} the laser energy was proportional to the partial pressure of NF 3 or H 2 . No change in slope of the laser energy versus pressure curve was observed in going from low-pressure nonexploding regimes to high-pressure exploding regimes, implying that the reactions causing the explosion did not contribute to the lasing. Lasing usually occurred in two peaks, the first containing HF(V=2) \rightarrow HF(V=1) lines and the second containing HF(V=3) \rightarrow HF(V=2) and HF(V=1) \rightarrow HF(V=0) lines. These data indicate that lasing is due to the reaction sequence: 1) NF_{3} + e^{-} = \cdot NF_{2} + F\cdot + e^{-}; 2) F\cdot + H_{2} = HF+(V) + H\cdot ; and 3) HF+(V) + h\nu = HF+(V-1) + 2h\nu .

Preparation and study of a series of borane and octahydrotriborate derivatives of methylated polyamines

Abstract A series of borane and octahydrotriborate derivatives of methylated polyamines has been prepared for the purpose of finding better neutron-shielding materials. The variance in certain chemical and physical properties with increasing chain length of the basic amines and with an increase in the number of carbon atoms between adjacent nitrogen atoms is discussed.

Preparation of fluoroborazines

Diborane was found to react with tetrafluorohydrazine at l40 to l60 deg C to yield a mixture of fluoroborazines (B/sub 3/N/sub 3/H/sub n/F/sub 6-n/) together with BF/sub 3/, B/sub 5/H/sub 9/,H/sub 2/,N/sub 2/, and BF/sub 3/NH/sub 3/. Yields of fluoroborazines varied from 5 to 20%. Preliminary separation of the reaction products was accomplished by high vacuum fractional condensation techniques using traps at -63, -78, and -196 deg C. The mass spectrum of the B/ sub 3/N/sub 3/H/sub 5/F fraction was found to be complex. The highest series of peaks began at a m/e of 92 and ended abruptly at 99. The mass spectrum of the B/ sub 3/N/sub 3/H/sub 4/F/sub 2/ fraction was similar to that of B/sub 3/N/sub 3/H/ sub 5/F with the exception of a series of peaks beginning at a m/e of 113 and ending abruptly at 117. It is believed that both fractions are mixtures of isomers. The hazards in working with the synthesis are also discusssd. (P.C.H.)

Preparing 10BCl3, 11BCl3, 10B35Cl3 and 11B35Cl3 by reacting B with AgCl

Abstract The reaction of AgCl with elemental B at 1133°K produces good yields of BCl 3 (77% based on B) when AgCl is in excess and produces especially good yields (96% based on AgCl) when B is in excess. This reaction is useful in preparing isotopically substituted BCl 3 .