Infrared Ni lines in the models s15p2 at 350 d. We show the quantity λF_λ using the total flux (solid) and that due to Ni only (dashed) centered at the rest wavelength of two strong lines of [Ni I] and [Ni II] (see label). A distance of 10 Mpc is assumed. The inset shows the Ni mass fraction versus velocity at 350 d, which thus accounts for all stable Ni isotopes (those that after explosion were neither ⁵⁶Ni nor ⁵⁷Ni – these arise here at an 80% level from ⁵⁸Ni). (See Section 3 for discussion.)