Analytical fit of the I-V characteristic for cylindrical and spherical probes in electronegative plasmas

This paper develops a theoretical model for the sheath that surrounds cylindrical and spherical Langmuir probes immersed in an electronegative plasma. The model allows the electric potential profile surrounding the negatively polarized probe, the densities of the different charged particles within the sheath, and the I-V characteristic curves to be determined for several negative ion density and temperature values. These curves are fitted analytically, permitting expressions to be obtained for the potential profile, the floating potential, and the sheath edge