Generation of negative ions from SF₆ gas by means of hot surface ionization

Abstract

Negative surface ionization on the hot filament is a relatively simple and effective method for carrying out negative ion formation studies. Eight SF(6) decomposition channels leading to the formation of negative ions have been detected and analyzed using this technique.

Atmospheric pressure anion mass spectrometry: electron affinities and activation energies of thermal electron attachment – perfluoromethylcyclohexane, C7F14

“…The vertical axes are electron intensities in arbitrary units from NPES or PD, log [electron intensities], the derivatives, d[NPES)] and the log [d(NPES)]. The plots clearly support multiple states reported using the NSI data from Pelc . Most significant is the 1.7 eV structure at the electron affinity reported in January 2015 …”

“…. The 2012 negative surface ionization, NSI, data reported by Pelc for SF 6 , SF 5 , SF 4 and F are the only mass‐analyzed data for electron attachment to SF 6 at temperatures above 1000K …”

“…These values were supported by the magnetron, Langmuir probe, and high‐temperature chemical modeling experimental facility data. Electron attachment to C 7 F 14 was also studied in the latter . By analogy it is proposed that the gs‐AE a (C 7 F 14 ) is about 3.0 eV and that the gs‐E 1 (C 7 F 14 ) is greater than 1.7 eV.…”

“…In 2014, we reported AE a (SF 6 ): (eV) 3.00(10), 2.60(10); 2.45(3); 2.20(3); 2.00(3); 1.80(3); 1.60(2);1.40(2); 1.03(3); 0.80(3); 0.65(3); 0.45(3); 0.25(3); 0.10(5) from negative surface ionization data, NSI, from 1000K to 2300K published by Pelc. The gs‐AE a SF n , 3.8 eV for odd n and 3.0 eV for even n, and dissociation energies of SF n 3.0 eV for odd n and 4.0 eV for even n from these data were used to calculate HIMPEC …”

Negative surface ionization electron affinities and activation energies of SFn

“…. We determined the AE a values: (eV) SF 6 , 3.0(1); SF 5 , 3.85(2); SF 4 , 2.7(1) from the decrease in the NSI data at temperatures above 2470 K . Here, we predict multiple AE a (SF n ) values (n = 1 to 6), given in Fig.…”