Influence of water vapor and decomposition products on the positive- and negative-ion spectra of SF6 corona.

摘要

We report on the positive- and negative-ion spectra obtained from in-situ mass spectrometric analyses of ions sampled from corona discharges in SF(sub 6) at P = 6.7 kPa (50 Torr). In positive-ion spectra the presence of water vapor results in the formation of water cluster ions of the form H(sup +)(H(sub 2)O)(sub n). The distribution of cluster sizes shifts to smaller clusters as the water vapor content decreases. In addition to the SF(sub 6) fragment ions (SF(sub 5)(sup +), SF(sub 3)(sup +), and SF(sub 2)(sup +)), which are observed under relatively dry conditions, the hydrated species SF(sub 5)(sup +)(H(sub 2)O) is observed down to water additions of only 40 ppM, the lowest concentration studied. In addition, the ion detected at mass 197 is believed to be the complex SF(sub 3)(sup +)(SF(sub 4)) where SF(sub 4) is an important neutral by-product of SF(sub 6) discharges. In negative-ion spectra, the influence of water vapor is manifested indirectly by the formation of HF clusters of the form F(sup (minus))(HF)(sub n). Other clustered species observed include OH(sup (minus))(H(sub 2)O)(sub n) and OH(sup (minus))(HF)(sub n). The role of other decomposition by-products, such as SOF(sub 4) and SO(sub 2), of SF(sub 6) corona on the positive- and negative-ion spectra will also be discussed. 11 refs., 6 figs., 1 tab.