Dispersed fluorescence studies of the diatomic molecules MoC, RuC, and PdC are reported. New states identified in MoC and RuC are the [...]2 delta (1)12 sigma (1), (3,1)Delta (2) states and the [...]2 delta (3)12 sigma (1), (1)Delta (2) state, respectively. Five states are observed by dispersed fluorescence in PdC. The ground state is found to be [...]2 delta (4)12 sigma (2), (1)Sigma (+), with the [...]2 delta (4)12 sigma (1)6 pi (1), (3)Pi (Omega) manifold of states lying about 2500 cm(-1) above the ground state. The [17.9]Omega =1 state of PdC is also identified as [...]2 delta (4)12 sigma (1)13 sigma (1), (3)Sigma (+)(Omega =1), corroborating recent results of resonant two photon ionization spectroscopy studies. The spin-orbit interactions of these molecules are analyzed to deduce the composition of the molecular orbitals, and comparisons are made to ab initio theory when possible. An examination of the trends in bond energy, bond length, and vibrational frequency among the 4d transition metal carbides is also provided. (C) 2001 American Institute of Physics.