Temperature dependence splitting

Table 2 Enantiomeric temperature-dependent splitting of trofosphamide.

A direct spectroscopic proof of the valence isomeric rectangular structure of cyclobutadiene [48] was obtained from the investigation of 1,2,3-tri-t-butyl-cyclobutadiene [49] in which one outer t-butyl group was perdeuteriated (Maier et al., 1982). The peak for the doubly populated olefinic site (C-l, C-3) in [49] shows a temperature dependent splitting of 0.453-0.297 ppm between -96°C and — 62°C, indicating isotopic perturbation of a fast equilibrium (46) of valence isomers. Carbon C-l substituted with the deuteriated t-butyl group is shifted upheld. 

Box, H.C. Radiation Effects, ESR and ENDOR Analysis. NewYork Academic Press, 1977. Sullivan, P.D., Menger, E.M. Temperature-Dependent Splitting Constants in the ESR Spectra of Organic Free Radicals. Adv. Magn. Reson. 9 (1977) 1. 

Fig. 53. The temperature dependence of 7", in tiglic acid. Methyl tunnel splitting (ueV)...

For example, octahedral quadrupole splitting observed for the cis-octahedral analogs 7,8). More recently, temperature-dependent Mossbauer measurements have been used in conjunction with Raman spectroscopy to determine molecular weights 453) and lattice rigidity 460) of various organotin compounds. 

Mo(V) paramagnetic species is also an argument to exclude an interaction between the Mo site and Fe-S center I. These studies were further complemented by detailed study of the observable splitting and its temperature dependence, EPR saturation, and the effect of differential reduction of the Fe-S centers. A magnetic interaction was also seen in xanthine oxidase, between various Mo(V) EPR species and one of the Fe-S centers. A study on the... 

An advanced subject in the theory of quadrupole splitting is the fact that the quadrupole splitting can become temperature dependent. At the heart of this effect is the change in Boltzmann populations of electronically nearly degenerate many-electron states with temperature. 

Further experimental examples of temperature-dependent and magnetically-induced quadrupole splittings are provided in the first volume of this book (Chap. 6, see CD-ROM, Part VI) and also in Sect. 9.4 in Chap. 9 of the present volume. 

Figure 6.13 shows the Mossbauer spectra of ferritin [51], which is an iron-storage protein consisting of an iron-rich core with a diameter around 8 nm with a structure similar to that of ferrihydrite and which is surrounded by a shell of organic material. At 4.2 K essentially all particles contribute to a magnetically split component, but at higher temperatures the spectra show the typical superposition of a doublet and a sextet with a temperature dependent area ratio. At 70 K the sextet has disappeared since all particles have fast superparamagnetic relaxation at this temperature. 

The temperature dependence of the magnetic hyperfine splitting in spectra of interacting nanoparticles may be described by a mean field model [75-77]. In this model it is assumed that the magnetic energy of a particle, p, with volume V and magnetic anisotropy constant K, and which interacts with its neighbor particles, q, can be written... 

Both Fe(ll)(TPP) and Fe(II)(OEP) have positive electric quadrupole splitting without significant temperature dependence which, however, cannot be satisfactorily explained within the crystal field model [117]. Spin-restricted and spin-unrestricted Xoi multiple scattering calculations revealed large asymmetry in the population of the valence orbitals and appreciable 4p contributions to the EFG [153] which then was further specified by ab initio and DFT calculations [154,155]. 

Temperature-Dependent Quadrupole Splitting in Paramagnetic (S = 2) Iron Compounds (Example Deoxymyoglobin)... 

Dynamically Induced Temperature-Dependence of Quadrupole Splitting (Example Oxymyoglohin)... 

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