Cross-sections of bound-free ${\rm I}_2 ( 0_g^ + , \mathop 1\nolimits_g (aa, ab)\buildrel{{\scriptstyle hv_{f}}}\over{\longleftarrow \!\!\!\! - \!\!\! - \!\!\! -}\mathop {B{\rm 0}}\nolimits_u^ + ,\;v_B = 18 - 21 )$ and bound–bound ${\rm I}_2 ( {\mathop 0\nolimits_g^ + , \mathop 1\nolimits_u (bb) \buildrel{{\scriptstyle hv_{f}}}\over{\longleftarrow \!\!\!\! - \!\!\! - \!\!\! -}\mathop {B{\rm 0}}\nolimits_u^ + , v_B = 21,\;J_B } )$ transitions at a fundamental harmonic of the Nd:YAG laser