F"= - ξ F'/2 → F"/F' = - ξ/2 → log(F') = - ξ^2/4 + C1 → F' = C2 exp(- ξ^2/4)
→ F = C2 ∫ exp(- ξ^2/4) dξ + C3 = C4 ∫ exp(- s^2) ds + C3