All of the hyperfine interactions associated with localized and delocalized electron spin in the four isotopes of the triatomic radical H2N are treated. With nuclear Zeeman energy included, the resulting magnetic-field-dependent nuclear spin states are used to calculate the energies and nuclear spin-state mixing of the nuclear levels and the corresponding hyperfine effects upon electron paramagnetic resonance (EPR) transition energies and nuclear state transition probabilities. In the absence of nuclear spin-state mixing there would be, for example, 10 EPR transitions in D2 15N and 15 in D2 14N, all ΔmI = 0 fully allowed. In the presence of mixing, there are 243 in D2 15N and 729 in D2 14N, with large differences in probability among transitions, many 0 or small. Because of numerous (at least partially allowed) transitions, spectra from isotopes of H2 N radicals are the superposition of signals at greatly different levels of saturation. In this report, EPR spectra from D2 15N models, with either N or 2D hyperfine interaction suppressed, are simulated as a function of microwave frequency and power × spin-lattice relaxation time product. A large range of microwave frequency (and, concomitantly, magnetic field strength) will be needed to evaluate the effect of the nuclear Zeeman energy. The experimental requirements for microwave power and low temperature (long spin-lattice relaxation rate) are quantified.PACS Nos.: 33.15.Pw, 33.35.+r, 33.25.+k
Supercooled high spin state in metallo-supramolecular assemblies
