The formation of a plasma by strong irradiation of mercury vapour with mercury lines

A plasma is shown to be present in mercury vapour which is irradiated with intense mercury lines. The source of ionisation is almost certainly associative ionisation by the reaction Hg(6 3 P 0 )+Hg(6 3 P 1 ) to Hg 2 + +e, forming the mercury molecular ion, The plasma is described by a collisional ion fluid model which enables an estimate to be made of the cross-section for this process of 3.7*10 -18 m 2 , based on measured plasma properties and excited state populations. The observed range of electron temperatures is predicted by a model of the energy balance between collisional and wall losses and superelastic collisional gains.