A mass spectrometric study of positive and negative ion formation in an SF₆corona. II. Influence of water and SF₆neutral by-products

For pt.I see ibid., vol.25, p.761 (1992). The effects of water and SF 6 by-products on both positive and negative ion formation in an SF 6 corona have been examined. For a positive corona for 'pure' SF 6 at p=6.5 kPa the primary ions observed are SF 5 + , SF 3 + and SF 2 + , with water addition (in the range 0-640 p.p.m.) ion conversion and clustering occurs leading to H + (H 2 O) n , (n=1-4), SF 5 + (H 2 O) n , (n=0-2), SOF 3 + (H 2 O) n , (n=0-2). For a negative corona for 'pure' SF 6 , the primary ions observed are SF 6 - , SF 5 - and F - , with water addition ion conversion and clustering also occurs leading to F - (HF) n , (n=0-4), OH - (H 2 O) n , (n=0-2), SOF 5 - (HF) n (n=0, 1), SF 6 - (HF) n , (n=0, 1), SO 2 F - and SO 2 F 2 - , where HF is a neutral by-product of the SF 6 /H 2 O corona. Of these ions OH - (H 2 O) n is considered a possible 'seed' ion for collisional electron detachment in an SF 6 /H 2 O corona. It is shown that by-product formation such as the production of SOF 4 , even when present at trace levels, will lead to significant modifications to the negative ion content.