Californium(II) iodide is a binary inorganic compound of californium and iodine with the formula .
It can be produced by reducing californium triiodide with hydrogen in a quartz thin tube at 570 ðC:
The compound forms a dark purple solid. At slightly higher temperatures, it melts and reacts with the silica in the thin tube, producing CfOI.
Californium diiodide has two crystal structures, one is -type crystal structure, stable at room temperature, with lattice parameters a = 743.4 ñ 1.1 pm and ñ = 35.83 ñ 0.07ð; the other is metastable, of -type with lattice parameters a = 455.7 ñ 0.4 pm and c = 699.2 ñ 0.6 pm. Californium diiodide has an absorption band in the wavelength range from 300 to 1100 nm, which proves the existence of Cf(II).