Studies of Atomic Recombination of Nitrogen, Hydrogen, and Oxygen by Paramagnetic Resonance

The three‐body volume recombination coefficient for neutral atoms A of nitrogen, oxygen, and hydrogen in their parent molecular gases M has been measured over a pressure range of one to ten millimeters at 300°K. The observations fit a reaction of the form $$\mathrm{A}+\mathrm{A}\mathrm{+[}\mathrm{M}\mathrm{]\to }{\displaystyle {lim}_{k_1(\mathrm{A})}}{\mathrm{A}}_2\mathrm{*+[}\mathrm{M}]$$ , where k₁(A), the rate constant, is found to be, respectively, k₁(N) = 1.5 × 10⁻³² cm⁶/sec, k₁(O) = 0.45 × 10⁻³² cm⁶/sec, and k₁(H) = 6.5 × 10⁻³² cm⁶/sec. These determinations have an experimental fluctuation of ± 20%. Observations of the electron spin resonance (ESR) signal from the ground state of the atoms allowed direct determination of the atomic density. Measurements were made in a stream of flowing gas which carried the atoms through the ESR detection cavity. An atomic concentration of 10¹⁴ − 10¹⁶ cm⁻³ could be obtained in a CW electrodeless discharge. Surface recombination was inhibited by coating wall surfaces with a thin film of concentrated H₂SO₄. The work also includes some preliminary measurements of surface atomic recombination coefficients.