The photon cascade emission of Gd 3 + ions under 8 S 7 / 2 -> 6 G J excitation is observed in GdBaB 9 O 1 6 . Under the 202 nm excitation, a red and a near infrared radiative transition from 6 G J states, 6 G J -> 6 I J and 6 G J -> 6 P J occur followed by an ultraviolet emission of 6 P J -> 8 S 7 / 2 . The absence of emission from 6 D J and 6 I J states is attributed to the effective multiphonon 6 D J -> 6 I J and I J -> 6 P J relaxation in this lattice.