13C nuclear spin

Here /, is the 13C nuclear spin, S is the unpaired electronic spin, and A j- is the Fermi contact hyperfine coupling tensor. This coupling is identical for all 13C nuclei as long as the C60 ion is spherical, but becomes different for different nuclei after the Jahn-Teller distortion leading to an inhomogeneous frequency distribution. The homogeneous width of the 13C NMR lines is, on the other hand, mainly determined by the electron-nuclear dipolar interaction... 

The NOE is an example of polarization transfer (or cross polarization), because polarization of one set of nuclear spin states (here, saturation of the H nuclei) results in the polarization of another set (here, the 13C nuclear spin states). The maximum Overhauser signal enhancement (q) is given by... 

Nuclear Overhauser effects (14) can arise from energy transfer from the proton nuclear spin reservoir to the 13c nuclear spin reservoir... 

The coherence time of electron spin of N-V center in pure diamond is defined dominantly by its interactions with the surrounding nuclear spins formed primarily by the spin-1/2 13C isotope. Recent spin-echo experiments [38] confirmed a basic idea of the single quantum object spectroscopy that each single object (electron spin of NV center) experiences its own meso-environment (set of nuclear spins) leading to the individual dynamical response for a selected center. As it was observed in [38] this environment is effectively separated into a set of individual proximal 13C nuclear spins, which are coupled coherendy to the electron spin, and the remainder of the 13C nuclear spins, which cause the loss of coherence. Information about hfi interactions between NV and 13C spins in different positions retrieved in these experiments can be clarified by ab initio (DFT) calculations [39]. Such calculations are also important for interpretation of electric field effects on single NV centers [34]. 

The first example concerns a system with an electron spin and a nuclear spin, and for simplicity we take S = 1/2 and / = 1/2. Actual examples would be localized radicals 13C or 15N", and mononuclear low-spin 57Fein or 183WV. The spin Hamiltonian is... 

An additional asset of both donors in silicon and NV centres is that nuclear spins, of 31P in the former and of N and neighbouring 13C in the latter, can be employed as long-term storage quantum memories [63], or even to build multiple qubit registers [22, 67]. 

The comparative study of the experimental NMR spectra of Zs-1-cyclopropyl -2-(triisopropylsilyl)ethyl cation (17) and the computational model structure E-1-cyclopropyl-2-(trimethylsilyl)ethyl cation (18) demonstrates another application of calculations of 3H and 13C NMR chemical shifts and nuclear spin-spin coupling constants. In particular vicinal3./(11,11) spin-spin coupling constants are useful for... 

Within meat science, NMR spectroscopy has mainly been carried out on 3H, 13C and 31P, which all are nuclei with a nuclear spin of /= 1/2. Most relevant data on each nucleus will be reviewed in the following. 

Dynamics of Poly(oxyethylene) Melts Comparison of 13C Nuclear Magnetic Resonance Spin-Lattice Relaxation and Dielectric Relaxation as Determined from Simulations and Experiments. 

In contrast to ESR spectroscopy, which can only be used to study species with unpaired electrons, NMR spectroscopy is applicable to the investigation of all polymer samples. Nuclei with non-zero total nuclear spin (e.g., 1H, l3C, 19F, 14N) will have a magnetic moment which will interact with an external magnetic field resulting in quantized energy levels. Transitions between these energy levels form the basis of NMR spectroscopy. 1H and 13C... 

Nuclear magnetic resonance (NMR) is a widely utilized technique, which detects the reorientation of nuclear spins in a magnetic field. It can potentially be used to determine the 3-D structure of the protein itself, as well as supplying information on kinetics and dynamics, ligand binding, determination of pK- values of individual amino acid residues, on electronic structure and magnetic properties, to mention only some of the applications. In addition, it can be selectively applied to specific nuclei—1H, 13C, 15N, 19F (often substituted for H as a... 

Cross-correlated dipolar relaxation can be measured between a variety of nuclei. The measurement requires two central nuclear spins, each of which is directly attached to a remote nuclear spin (Fig. 16.4). The central spin and its attached remote spin must be connected via a large scalar coupling, and the remote spin must be the primary source of dipolar relaxation for the central spin. The two central spins do not need to be scalar coupled, although the necessity to create multiple quantum coherence between them requires them to be close together in a scalar or dipolar coupled network. In practice, the central spins will be heteroatoms (e.g. 13C or 15N in isotopically enriched biomolecules), and the remote spins will be their directly attached protons. 

It is inappropriate here to discuss details of nmr spectroscopy. However, the full possibilities for structural studies arise from the use of probes that bind to the molecule under study and perturb the nmr spectrum. These probes are generally paramagnetic species, in particular the lanthanide cations. In the nmr spectrum separate signals arise from each nucleus in the molecule, provided that the nucleus possesses a nonzero nuclear spin (e.g., H, 13C, 14N). The extent of the spectral perturbations of a given signal depends on the relative geometries of the paramagnetic species and the nucleus in question. Thus structural parameters can be obtained, in principle, for most atoms (nuclei) in a protein molecule.5... 

---