Analysis of Single Crystal Spectra

Paramagnetic species trapped in solid materials usually possess anisotropic g- and hyperfine couplings. Zero-field splittings occur when 5 V2. The spin Hamiltonian formalism described in Appendix A3.1 is a convenient means to summarise the different interactions. The following spin-Hamiltonian is adequate to illustrate most aspects of the analysis. 

---

Second order splittings in solutions Analysis of single crystal spectra Exchange effects Analysis of asymmetric lines Analysis of asymmetric lines... 

Analysis of NMR spectra from the stepped rotation of a single-crystal sample is the most rigorous manner in which to characterize the tensor interactions associated with a particular nucleus. Particularly, the orientation of the PAS of an interaction tensor with respect to the molecular framework can be precisely determined. The methods of analysis of single-crystal NMR data have been reported elsewhere. While once more common, single-crystal analyses of quadrupolar halogens in diamagnetic samples are no longer as frequently... 

Abstract The analysis of ESR, ENDOR, and ESEEM data to extract the resonance parameters is treated. Free radicals in solution are mainly identified by their hyper-fine couplings (hfc). The analysis of ESR and ENDOR spectra by visual inspection and by computer simulation is discussed. The Schonland method to obtain the principal values and directions of the anisotropic g- and hfc- tensors from single crystal ESR and ENDOR data is presented. The modifications needed when 5 > A or / > A to obtain zero-field splitting ( i) or nuclear quadrupole coupling (nqc) tensors are considered. Examples of simulations to extract g-, hfc-, Tfs-, and n c-tensors from ESR and ENDOR spectra of disordered systems are presented. Simulation methods in pulsed ESR (1- and 2-dimensional ESEEM) studies are exemplified. Internet addresses for down-loading software for the simulation of ESR, ENDOR, and ESEEM spectra are provided. Software for the analysis of single crystal data by the Schonland method is also available. 

Spectroscopic analysis of Pu5+ and Pu6+ halides is in its initial stages. No low-temperature single-crystal spectra have been reported. A 25°C mull spectrum of the compound Rb2PuF7 was described earlier (37), and is now supplemented by the results for CsPuFg (31) PuF gas-phase spectra have been reported by several different groups at ANL (38-39). 

We discussed above the analysis of core-level spectra from cuprates which contain only a single hole in the d-band per Cu ion. This makes an irrelevant parameter within an impurity model. However, analysis can also be carried out for systems where [7dd plays a significant role. This is illustrated by the analysis of the core-level spectrum of LaCoOj carried out within the impurity model (Chainani et al, 1992). This oxide is modelled by the (CoOg) cluster with the transition-metal ion being formally in the 3 + oxidation state and in an octahedral crystal field. One has to therefore take into account interactions between various configurations such as d >, d Z, > >. ... 

A detailed analysis of the fine shapes of the spectra of single crystals of Mnl2,... 

We have measured the EER spectra of single crystal CdSe in a polysulfide electrolyte using the same configuration for which the relaxation spectrum analysis was applied. Preliminary results are shown in Fig. 6. 

We report an electron spin resonance (ESR) study on a C60 anion and a metal (M) encapsulated in fullerene (C ) (a metallofullerene M C ). The anisotropy components of the g-factor of Cg0 were determined accurately from the analysis of angular-dependent ESR spectra of single crystal Cg0 salt. The evaluation of the g-factor was performed according to the classification of symmetry of the C60 geometry. It was found out from the evaluation that the molecular structure of Cg0 should he distorted to lower symmetry, C2h or C,. The variety of ESR spectra of metallofullerenes of La C s was obtained in terms of a g-factor, a hyperfine coupling constant, and a line width. In the case of the isomer I of La C80 and the isomer II of La C84, an abnormally large line width was measured. The molecular structure with high symmetry would reflect on the specific spin dynamics. 

---