Zero field spectrum

The value is derived from a zero-field spectrum recorded at 150 K. A q could not be determined at 4.2 K because the compound is in the limit of slow paramagnetic relaxation and the strong unquenched orbital moment forces the internal field into the direction of an easy axis of magnetization. As a consequence, the quadrupole shift observed in the magnetically split spectra results only from the component of the EFG along the internal field and the orientation of the EFG is not readily known dbabh is a bulky N-coordinating amide... 

Fig. 22.9 (a) Photoabsorption spectrum observed in zero field, using excitation path A of Fig. 22.8. (b) Same as (a), but observed at an applied dc electric field of 4.8 kV/cm. (c) Zero field spectrum observed using path B of Fig. 22.8. (d) Same as (c), but with an applied field... 

Fig. 6.14. Semilogarithmic pulsed field positron lifetime spectra corresponding to different values of T (indicated by the arrows) for a mean field of 41 V cm-1. (A spectrum with a d.c. field is also shown.) The numbers on the left are the numbers of coincidences for the first plotted point and the broken lines indicate the cut-off times rc where the spectra depart from the zero-field spectrum. Reprinted from Physical Review Letters 56, Tawel and Canter, Observation of a positron mobility threshold in gaseous helium, 2322-2325, copyright 1986 by the American Physical Society.

FIGURE 2.12 Mossbauer spectra of intermediate X recorded at 4.2K for B = 0. (a) Earlier preparation containing a large fraction of diferric species, outlined by the solid curve. The two minor lines, indicated by the arrows, belong to sites a and b of X. (b) Zero-field spectrum of X, from a later sample, obtained by subtracting two contaminants as described in the text. Dashed line belongs to site a. 

Our theoretical analysis of the zero field spectrum is directed towards a quantitative understanding of the most recent results. 

Mossbauer spectra for mycobactin P, a growth factor (sideramine) for mycobacterium Phlei, which is slightly soluble in ethanol were observed at 4.2 K (Fig. 8), and the spin Hamiltonian parameters D, X, /i, A and P were found to give a reasonably good simulation of the data (37). Notice the effect of the applied field in stablizing the spin states as evidenced by the decrease in the broad background of the zero field spectrum. 

High-resolution measurements of the discrete spectrum of donors in high-purity GaAs and InP have been performed by PTIS and in most cases, the spectra have been obtained under a magnetic field to reduce the spatial amplitude of the wave function, in order to limit the interaction between the electrons bound to neighbouring donors. With the application of a magnetic field, the FWHMs of the individual lines are drastically reduced and a comparison with the zero-field spectrum can be made in Fig. 6.41a, b. 

The best fit of the zero-field spectrum was obtained by introducing four different iron sites. The obtained parameters are listed in Table 12.1. Since no reference sample was used, the absolute isomer shift information cannot be obtained. However, the relative isomer shift of each iron site can still be obtained by setting one of the four sites as a reference. The best fit gave four quadrupole splittings as 1.48, 1.29, I. I, and 0.63 mm s . The relative isomer shift of the last three sites relative to the first site were —0.007, 0.012, and 0.042 mm s , indicating they have very similar isomer shifts. These values are consistent with the zero-field 80 K Mossbauer measurement on the same sample (the inset of Fig. 12.8a), where the four quadrupole splittings were 1.40, 1.13,0.84, and 0.54 mm s , the corresponding isomer shifts were 0.42,... 

---