The optical spectrum of diatomic RuC has been recorded from 17 800 to 24 200 cm-1. Three previously unidentified excited electronic states were analyzed and identified as having Omega'=0, Omega'=2, and Omega'=3. The Omega'=3 state was determined to be a (3)Delta(3) state that is suggested to arise from a mixture of the 10sigma(2)11sigma(2)5pi(3)2delta(3)12sigma(1)6pi(1) and 10sigma(2)11sigma(1)5pi(3)2delta(3)12sigma(2)6pi(1) electronic configurations. Three additional bands belonging to the previously observed [18.1] (1)Pi<--X (1)Sigma(+) system were analyzed to obtain B-e(')=0.558 244(48) cm(-1), alpha(e)(')=0.004 655(27) cm(-1), omega(e)(')=887.201(37) cm(-1), and omega(e)(')x(e)(')=5.589(7) cm(-1) for the Ru-102 C-12 isotopomer (1sigma error limits). A Rydberg-Klein-Rees analysis was then performed using the determined spectroscopic constants of the [18.1] (1)Pi state, and similar analyses were performed for the previously observed states. The resulting potential energy curves are provided for the Ru-100 C-12, Ru-101 C-12, Ru-102 C-12, and Ru-104 C-12 isotopic species. (C) 2004 American Institute of Physics.