We report the first observation of collision induced state-to-state energy transfer from the 2(u) (D-1(2)) (v(2u) = 3-7) ion-pair state of I-2 using a perturbation facilitated optical-optical double resonance technique through the c(1)Pi(g) similar to B (3)Pi(0(u)(+)) hyperfine mixed double-faced valence state as the intermediate state. The excitation of the 2(u) (D-1(2)) state yielded the weak UV fluorescence from the wide range of vibrational levels in the nearby 2(u) (D-1(2)) state. The vibrational distribution in the 2(g) (D-1(2)) state derived by the Franck-Condon simulation of the UV fluorescence showed that the population in the 2(u) (D-1(2)) state transfers mostly to the 2(u) (D-1(2)) vibronic levels which are located energetically above the laser-prepared level. The radiative lifetimes and the self quenching rate constants were determined to be 21.3 +/- 0.1 and 44.6 +/- 0.8 ns, and (1.30 +/- 0.01) x 10(-9) and (2.26 +/- 0.17) x 10(-9) cm(3) molecule(-1) s(-1) for the 2(u) (D-1(2)) (v(2u) = 3) and 2(u) (D-1(2)) (v(2g) = 5) states, respectively. The rate constant for the 2(u) (D-1(2)) - 2(g) (D-1(2)) collision induced state-to-state energy transfer was also evaluated to be (1.89 +/- 0.01), (3.07 +/- 0.07), and (3.77 +/- 0.05) x 10(-19) cm(3) molecule(-1) s(-1) for the v(2u) = 3, 5, and 7 levels, respectively. The very large self-quenching cross sections for the ion-pair states of I-2 could be explained by the harpoon mechanism.