Temperature-dependent quadrupole splitting

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

Fig. 15. Temperature dependent quadrupole splitting of PBLG-Kdi (open triangle) and PBLG-fd2 (filled triangle). Reproduced with permission from the Society of polymer Science, Japan.

Fig. 21. Crystal field results for the temperature dependent quadrupole splitting in Hb, involving spin-orbit interaction between energetically low lying levels r>Bg, 3E, Mi, and 5E. Their energies relative to the groundstate 5B2 are (for E (3E), E (Mi), and E (s ) in cm-1) ...

Fig. 25. Temperature dependent quadrupole splittings for model (3). A = 90 cm-1. Experimental A Eq(T) data for frozen Mb solution [Ref. (53)] are indicated by closed circles, for a Mb single crystal [Ref. (42)] by "x and error bars, and for frozen Hb (rat) solution [Ref. (52)] by open circles and error bars. Energies 5B%, bB ], bA 2, and Mi in cm-1 corresponding to AEq(T) curves are ...

Fig. 26. Temperature dependent quadrupole splittings for model (2). A = 90 cm-1. Experimental AEq(T) data are defined in Fig. 25. Energies for 5B2, bB, A and 1A1 in cm-1 corresponding to AEq curves are ...

The measurement of a small distortion in the tetrahedral FeCU " ion was first reported by Gibb and Greenwood [35]. The level is split by a tetragonal distortion in the crystal field and this results in a markedly temperature-dependent quadrupole splitting as the thermal population of the and d,. levels changes (see Fig. 6.9). A more extensive investigation [36] has shown... 

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. 

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. 

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]. 

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

The temperature dependence of the isomer shift and quadrupole splitting for the high-spin and low-spin iron(II) states in [Fe(HC(3,5-(CH3)2pz)3)2](BF4)2 and details of the fits and their temperature dependence may be found elsewhere [46]. The extent of the spin-state crossover is shown in Fig. 18, a figure which clearly indicates that the spin-state crossover in [Fe(HC(3,5-(CH3)2pz)3)2](BF4)2 stops at 50 percent. In contrast it should be noted that, in the structurally very similar [Fe(HC(3,5-(CH3)2pz)3)2]l2 complex, [49] the spin-state crossover is 100 percent complete at 4.2 K. 

Fig. 7. Temperature dependence of the quadrupole splitting for the inner (circle) and the outer (triangle) of PBLG-d5.

---