Detailed studies of I ₂(β1 _g , v _β = 13, J _β ∼ v _D = 12, J _D and D, 48, J _D ∼ β, 47, J _β) rovibronic state coupling have been carried out using two-step two-color, hν ₁ + hν ₂ and hν ₁ + 2hν ₂, optical-optical double resonance excitation schemes, respectively. The hyperfine interaction satisfying the = 0, 1 selection rules (magnetic-dipole interaction) has been observed. No electric-quadrupole hyperfine coupling ( = 2) has been found. The dependences of ratios of luminescence intensities from the rovibronic states populated due to the hyperfine coupling to those from optically populated ones on energy gaps between these states have been experimentally determined. The matrix elements as well as the hyperfine structure constant have been obtained using these dependences. It is shown that they increase slightly with the vibrational quantum number of the states.