Fluorescence (phosphorescence) excitation spectra as well as luminescence spectra and decay times were investigated for NO in N2 and mixed N2/Kr matrixes. All Rydberg states rapidly relax to the ground state in mixed matrixes with the N2 molar fraction exceeding cN2 = 0.35. This dependence on the N2 concn. is attributed to the complete fluorescence quenching of all NO mols. with at least one N2 nearest neighbor. The vibrational levels of the B 2P valence states strongly coupled to the Rydberg state are also depopulated. The general picture of relaxation channels is discussed. [on SciFinder (R)]