New time and energy resolved spectra of the L' 2F-X 2P(0,v") bands of NO in Ar and Kr matrixes are reported. The L'(0,v") bands are excited exclusively via the B' 2D valence state and their lifetime is 3000 +- 500 ns in both matrixes. The quantum efficiency for L'(v = 0) emission is estd. as ?0.04. The 2F-2P transition is discussed in terms of a statically induced transition moment involving spin-orbit mixing with B' 2D, but also in terms of nonadiabatic matrix elements due to the coupling to the lattice. Relaxation down to L'(v = 0) is discussed in terms of matrix-induced interstate cascading with the b 4S- state. [on SciFinder (R)]