キシレンによるN2(A3Σu+)の失活とキシレン分解生成物の陰極表面への付着による電流阻止作用

概要

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The collisional quenching rate coefficient of metastable nitrogen molecules N2(A3Σu+) by m-xylene (C8H10) is determined experimentally in the Townsend discharge. The diffusion coefficient of N2(A3Σu+), and the reflection coefficient of N2(A3Σu+) at the electrode surface are also determined simultaneously. During the experiment, we find that it is difficult to continue the current measurement necessary to determine the fundamental constants of N2(A3Σu+) for long period. It is considered that any by-product of xylene would be decomposed by N2(A3Σu+) is deposited on the cathode, through repeated experiments, then the current-voltage curves consistently shift to the higher-E/p0 region. For the purpose of clarifying the reason behind this behavior, we confirm that these changes are caused by the current prevention by the decreases of initial photoemission current from the cathode and the decrease in the secondary ionization coefficient γ, because the cathode surface is covered by deposition film of a by-product of decomposed xylene.