The resonance enhanced two photon ionization (RE2PI) study of $Rb_2$ near 21000 $cm^{-1}$ identified five electronic states although there are only two 2 $^1Π_u$ - X $^1Σ_g^+$ and 2 $^1Σ_u^+$ - X $^Σ_g^+$ allowed transitions. Because the spin-forbidden transitions borrow their intensities from the allowed transitions through the spin-orbit coupling, the triplet states (the 2 $^Π_u$ and 3 $^3Σ_u^+$ states) can be observed. The Λ-splitting of the 2 $^1Π_u$ state are originated from the L-uncoupling interaction with the $^1Σ_u^+$ state. The 2 $^1\Sigma_u^+$ state shows characteristic features of the double minimum potential and an ion-pair state. We also observe the predissociation of the 2 $^1Π_u(1_u)$, 2 $^Π_u$ $(1_u)$ and 2 $^1Π_u^+(0_u^+)$ states by the repulsive 2 $^3\Sigma_u^+$$(1_u)$ state.
