The behavior of nitrogen, hydrogen, and deuterium atoms trapped from the gaseous phase and matrix-isolated in solid molecular hydrogen are studied by the EPR method. It is established that all these atoms are localized in the substitutional position of the matrix crystal lattice. The linewidths in the EPR spectrum of nitrogen are found to be one fourth of the linewidths recorded by most authors. It is shown that a version of theoretical calculation gives a linewidth matching with the experimental value. It is proposed that two different types of matrix surroundings are possible for a nitrogen atom trapped in the substitutional position, one of which corresponding to the undistorted crystal lattice ofN2.The EPR line broadening under the action of zero-point atomic vibrations is observed for hydrogen and deuterium atoms. The magnitude and temperature dependence of the spin-lattice relaxation time for N, H, and D atoms in the solidN2matrix are obtained experimentally. ©1998 American Institute of Physics.