Nuclear-hyperfine splitting

Perhaps the best example of a well-defined nuclear hyperfine splitting in a hemoprotein is the Mossbauer spectra of cytochrome c peroxidase-... 

Nuclear hyperfine splittings in the rotational spectra of dimers have been observed in the molecular beam electric resonance experiments and the Fourier transform microwave experiments. In most cases, the coupling constants are interpreted with the simplified expression given in Eqn. (6) for axially symmetric molecules in the K=0 rotational manifold. Thus both the nuclear quadrupole coupling term and the... 

Figure 1.5. Nuclear hyperfine splitting of the J = 1 rotational level of CsF. The major splitting is the result of the 133Cs quadrupole interaction, and the smaller doublet splitting is caused by the 19F interaction (see text).

Inequations (7.155) and (7.158) we have taken the diagonal = 0 component of the second-rank spherical tensors T2(/ . S) and T2(/a, Ia). In general, these interactions and others like them will have off-diagonal terms also, with q = 1 and 2. The q = 2 components are particularly interesting because, for a molecule in a Id electronic state, they connect the A = +1) and A = — 1) components directly. They therefore make additional hyperfine contributions to the /I-doubling of molecules in Id electronic states. As a result, the nuclear hyperfine splitting of one component of a A-doublet is different from that of the other component. The two contributions are ... 

Lichten [3 5] studied the magnetic resonance spectrum of the para-H2, N = 2 level, and was able to determine the zero-field spin-spin and spin-orbit parameters we will describe how this was done below. Before we come to that we note, from table 8.6, that in TV = 2 it is not possible to separate Xo and X2. Measurements of the relative energies of the J spin components in TV = 2 give values of Xo + fo(iX2, and the spin-orbit constant A the spin rotation constant y is too small to be determined. In figure 8.18 we show a diagram of the lower rotational levels for both para- and ortho-H2 in its c3 nu state, which illustrates the difference between the two forms of H2. This diagram does not show any details of the nuclear hyperfine splitting, which we will come to in due course. 

Figure 8.41. 7Li nuclear hyperfine splitting of the J = 5/2 yl-doublet levels of LiO, and the types of transitions detected in the electric resonance experiments [112]. The electric dipole transitions obey the selection rules AJ = 0, AF = 0, 1 and all ten transitions shown were observed experimentally. 

Figure 10.61. Lower rotational levels of the CH radical, with Hund s case (b) labels. Each level actually possesses Tl-doublet and nuclear hyperfine splitting, which is not shown in this diagram. Note that the spin-rotation splitting decreases with N, in accordance with equation (9.81).

The YO molecule in its X 2S+ ground state was the subject of earlier radioffequency/optical double resonance studies by Childs, Poulsen and Steimle [81], who made observations for v = 0 to 4 and N values up to 91. The spin-rotation and nuclear hyperfine splitting for each rotational level takes a simple form the largest interaction is the 89Y Fermi contact interaction, so that the case (b) coupling scheme most appropriate is... 

Figure 11.44. Energy level diagram [87], including 139La nuclear hyperfine splitting, and transitions corresponding to the spectrum shown in figure 11.43.

An energy level diagram showing the nuclear hyperfine splitting of the 17,1 level is shown in figure 11.47. The most suitable coupling scheme is... 

The other main feature of ESR spectra arises from interaction of the unpaired electron with magnetic nuclei. The effect is known as nuclear hyperfine splitting, as the ESR line is split into a number of equally spaced components which depend on the spin of the nucleus. 

---