Comment on 'The equations for electronegative plasmas are not singular at the plasma centre at low pressures' by R N Franklin

摘要

Franklin's criticism (Franklin R N 2005 J. Phys. D: Appl. Phys. 38 2790) of our previous paper (Lampe M et al 2004 Plasma Sources Sci. Technol. 13 15 - 26) is based on three arguments: (1) that the limit of weak attachment is equivalent to low pressure, where our model is inappropriate; (2) that our use of the T-n -> 0 limit is inappropriate; (3) that the negative ion density n(n) is never singular at the centre. We point out that the weak attachment limit also corresponds (at high pressure) to low fraction of attaching gas, give conditions for the T-n -> 0 limit and discuss its consequences, and reiterate that we never argued that n(n)(0) is infinite, but rather discussed a quite different type of singularity.