Matrix Perturbations of the ESR of Trapped H, N, P, and As Atoms at 4.2°K

Electron-spin-resonance spectra of N, P, As, and H atoms trapped in matrices formed from rare-gas elements at 4.2°K have been studied. The isotropic hyperfine coupling of N and P increases with the atomic number of the matrix element whereas that of As decreases. The van der Waals interaction theory devised by Adrian to explain the matrix effects on the nitrogen hyperfine splitting was generalized and applied with good success to the heavier group-V atoms. The results indicate that these group-V atoms occupy substitutional lattice sites, whereas the H atoms occupy octahedral sites. Recalculation of the matrix perturbations on nitrogen with more recent analytical self-consistent-field wave functions significantly improved agreement between theory and experiment. The isotropic $g$ factor of N, P, and As was found to be less than the free-spin $g$ and to decrease with increasing atomic number of the matrix elements. A weak fine structure observed for As atoms trapped in the Kr matrix is attributed to a small fraction of the atoms trapped in crystalline faults in the matrix.