Robert K. Gould

Kinetics of CH4 formation from the reaction of H with graphite

Small ribbon‐shaped samples of spectroscopic grade graphite heated to between 500 and 1250 K have been exposed to atomic hydrogen produced by thermal dissociation of H2 on hot W and the rate of CH4 evolution has been measured mass spectrometrically. H2 pressures were between 1×10−6 and 5×10−5 Torr and arrival rates of H at the graphite surface ranged from 1×1014 to 5×1015 atoms cm−2 sec−1. When a well outgassed graphite surface is initially exposed to H atoms, the rate of CH4 evolution, NM, peaks and then decays to a steady‐state rate. A mechanism is proposed and examined which adequately explains the results observed. The mechanism involves the formation of a CH4‐producing surface complex by the reaction of an incident H atom with chemisorbed H atoms on the graphite surface. Additional chemisorbed H rapidly reacts with this complex and CH4 desorbs. The decay in NM to a steady‐state evolution rate is apparently caused by a surface reaction in which pairs of the surface complexes responsible for CH4 evolut...

Mass spectrometric analyzer for individual aerosol particles

A new analytical instrument has been developed to give real‐time chemical composition and size data on individual aerosol particles. It separates the particles from the entraining gases by means of aerodynamic nozzles and differential pumping, so that they enter the high vacuum region as a collimated beam. Each arriving particle is flash vaporized, the vapor ionized, and the ions analyzed by a quadrupole mass spectrometer. The instrument has been tested with several inorganic and organic aerosols and has yielded mass spectral peaks corresponding to a series of fragment ions. The more stable compounds yielded the parent ion as well. Particles 0.9 μm in diameter are readily detected with signal‐to‐noise ratios of 12:1 on the dominant peak. On this basis, the small‐size sensitivity limit is well under 0.5 μm diameter and, with design improvements, can probably be extended to 0.1 μm or smaller.

HTFFR kinetic studies of the fate of excited BaO formed in the Ba/N2O chemiluminescent reaction

Rate coefficients for quenching kQ and intersystem conversion kT of excited BaO formed in the reaction Ba+N2O(1)→BaO+N2 have been measured for several collision partners. Methods are developed and applied here for obtaining quenching rate coefficients in chemiluminescent reactions involving a reservoir state. Experiments were performed between 450 and 1000 K at 1–120 Torr in a modified high‐temperature fast‐flow reactor (HTFFR). The rate coefficients (or their upper limits) are, in ml molecule−1 s−1 units: kArQ (600–1000 K) ?3×10−13; kHeQ (460 K) <3×10−13; kN2Q (600 K) = (4.8±2.0) ×10−12; kN2OQ (600 K) = (4.2±1.0) ×10−10; 2.5×10−10?kO2Q (600 K) ?7.0×10−10; kArT (600 K) ?1.5×10−11. Incidental data at ?1000 K indicate that k1?5×10−11, and that the Ba/O2 reaction has about the same rate coefficient. In addition to BaO emission, strong Ba atomic emission arising from energy transfer processes was observed for [Ba]≳1×1013 ml−1 at T?1000 K. Measurements of the spectral distributions of the Ba/N2O chemiluminesce...

Electron attachment kinetics in flames: Dissociative attachment to HBO2

Abstract The rate coefficient for the dissociative electron attachment e + HBO 2 → BO 2 − + H has been measured in a number of well characterized laboratory test flames at total pressures of 1.0 and 0.13 atm. The data are consistent with the Arrhenius expression k = 3.2 × 10 −10 exp(−11000/ T ) ml molecule −1 s −1 between 1730 and 2250 K. The failure of the observed BO 2 − formation rates to correlate in any systematic way with hypothetical three-body rate coefficients demonstrates that three-body attachment processes are negligible in these flames and that dissociative attachment dominates.

Electron attachment kinetics in flames. II. Dissociative attachment to HCl

This work comprises the first direct determination of the kinetics of Cl− formation in flames. The experiments involve mass spectrometric measurements of negative ion concentrations as functions of flow time in the burned gases of well‐characterized laboratory test flames seeded with small quantities of alkali metals and chlorine compounds. The results are consistent with the two‐body dissociative attachment mechanism e+HCl→Cl−+H with a rate coefficient well represented by the Arrhenius expression k=6×10−11 exp(−10 100/T) ml molecule−1 s−1 over the temperature range 1730 to 2475 K. The flames are operated at pressures of 100 and 760 Torr. Electron concentrations were measured using a microwave resonance cavity method and positive ion profiles (total charged species) were determined with electrostatic probes. H‐atom concentration profiles required to take account of the reverse detachment process are well known for the 760 Torr flames; in the low pressure flames they were obtained using a mass spectrometri...

On electron attachment to HBO2: A comment

Abstract It has been pointed out that the attachment reaction e + HBO2 → BO−2 + H is close to or at equilibrium throughout large regions of the high temperature test flames in which its rate coefficient was determined. This is indeed the case but only in the later stages of the flames; the rate constant is derived from species concentration measurements in the early parts of the flames prior to the attainment of equilibrium.