Formation of Negative Ions in SbCl3

The formation of negative ions in SbCl3 by low-energy electrons has been investigated using a modification of a total ionization tube which allows the ion species to be determined and prevents contact potentials from affecting the electron energy in the collision region. The identification of the specific reaction taking place was obtained by modifying the total ionization tube to operate as a magnetron beyond cutoff. The mass of the ion species was then determined from an analysis of the ion current to the collector as a function of the applied axial magnetic field and the ion collector bias. The electron-energy distribution had an effective width at half-height of approximately 0.07 eV which was obtained using the retarding potential difference method. With the apparatus the most probable initial ion reaction was SbCl3+e→SbCl2+Cl—. The value of the dissociative capture cross section at the point of ion apparance was (1.8±0.3) × 10—16 cm2, and the minimum energy of the electron for the appearance of ions was approximately 0.01 eV at a gas temperature range 25°—50°C. The dissociation energy for the reaction SbCl3→SbCl2+Cl was 3.69±0.15 eV.