In a microplasma in Ar confined at atmospheric pressure, driven at 13.56 MHz, we theoretically investigate the whole structure of a lowtemperature plasma including the local distribution in gas temperature inside and outside a microcell. The governing equation of gas and wall temperature is combined with our original relaxation continuum model of an rf plasma. We demonstrate that electrons with intermediate energy play an important role in plasma production through stepwise ionization and metastable pooling in the presence of high-density metastables. Next, we examine the enhancement of the net ionization rate through the increase in the local reduced field under a broad minimum of the heated gas density. The atmospheric-pressure microcell plasma will be classified into a new spatiotemporal sustaining mechanism in the capacitively coupled plasma at 13.56MHz. This work predicts the presence of a nonequilibrium, steady plasma in a microcell even at atmospheric pressure in Ar under appropriate conditions.
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