[en] We have established a general relation for the expression of the internal conversion of an M₁ transition a 1s electronic state to an empty ns electronic bound state. Under the hypothesis that the density of the electron level ρ_n satisfies the condition ρ_nΓ >> 1 (where Γ is the total width of the excited atomic state) a calculation in the first order gives a relation for the internal conversion coefficient.This relation shows that the internal conversion coefficient takes a resonant character when the nuclear energy transition is smaller than the binding energy of the 1s electron. An application of this relation to an M₁ transition in the case of the ion ¹²⁵T_e with a charge state Q = 45 and an 1s electron binding energy E_B⁴⁵ = 35.581 KeV gives the value for the internal conversion coefficient R = 5.7