A new electronic transition of K-2 is identified near 500 nm by resonance enhanced two photon ionization study. The rotational structure shows O, P, Q, R, and S branches. We obtain molecular constants for the upper electronic state of K-39(2) as omega(e) = 79.22 +/- 0.02 cm(-1), omega(e)x(e) = 0.189 +/- 0.002 cm(-1), T-e = 19 855.74 +/- 0.02 cm(-1), B-0' = (5.181 05 +/- 0.000 06) x 10(-2) cm(-1), and D-0(') = (8.65 +/- 0.03) x 10(-8) cm(-1). By comparison with the ab initio calculated values and from other experimental evidence we assign the observed bands to the 1 (1)Delta(g)-X (1)Sigma(g)(+) transitions of K-2, which are allowed by electric quadrupole radiation.