The A(2)Delta-X(2)Pi and B(2)Sigma(-)-X(2)Pi transitions of CH/D were examined for radicals trapped in Ar and Kr matrixes. Excitation spectra yield further evidence that CH/D(B) rotates in solid Ar and Kr. Vibrational relaxation of CH/D(B) is faster for the heavier isotope, indicating that vibration to rotation energy transfer is the dominant mechanism. The decay of CH(B), nu = 0 is primarily radiative in both Ar and Kr, with small contributions from B --> A nonradiative transfer. Fluorescence was not detected from CD(B), nu = 0 as the B --> A transfer process was much faster than radiative decay for this isotope. The proximity of the CD(B), nu = 0 and (A), nu = 1 levels is responsible for the accelerated transfer rate. Spectra for the A-X transition of CH-Ar-n clusters were recorded for comparison with the matrix data. Relative to free CH, the transition is blue-shifted in the cluster and red-shifted in an Ar matrix. This contrast suggests that the clusters consist of CH bound to the surface of Ar-n.