Electron spin resonance of NO2

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Abstract
This study presents the results of an E.S.R. study of NO2 embedded in polycrystalline solid N2O4 at 77°k. The radicals were generated by u.v. photolysis of the host matrix. By proper choice of the experimental conditions, spectra can be obtained from which the same information about the NO2 molecule can be derived as from single crystal measurements, except for its spatial orientation(s) in the host matrix. The second-order solution of the hamiltonian describing the system is tractable for the relative spatial orientations and experimental results can be analysed easily. The magnetic parameters obtained from this second-order analysis are used for the calculation of the spin density distribution over the molecule, providing a check on existing electronic models for NO2. A comparison of these magnetic parameters with those of NO2 in other media shows that the interaction of the electron cloud of the radical with the environment depends on the type of host matrix that is used. Furthermore, the analysis of the spectrum is completed by computer simulation. Excellent agreement between theory and experimental results is obtained.