Transfer of coherence

In a heteronuclear nOe experiment, the first step may be identical to the homonuclear nOe experiment (i.e., involving an incoherent transfer of coherence from H to H/), while the second step could involve a coherence transfer from H to C nucleus by an INEPT sequence. These methods suffer from poor sensitivity and have therefore not been used extensively. 

Coherence transfer The transfer of coherence between two different types of nuclei. 

The HMBC-RELAY experiment has merit, but suffers from several deficiencies. First, 2/ch signals for quaternary carbons are missing since the transfer of coherences from carbon to protons is restricted to protonbearing carbons. This is also the drawback of the 2/,3/-HMBC experiment. 

Thus, an exchange between two-qubit entanglement and system-bath entanglement may take place and be dynamically controlled by modulations. If the systems couple to two baths that have common modes, one can observe the transfer of coherence and buildup of entanglement between the two systems via these modes. If, on the other hand, the baths were completely separate, the coherence transfer between each system and its bath can modulate the amount of system-system entanglement, first lost and then regained. 

The appearance of a homonuclear 2D spectrum is different from what you have seen for HETCOR, the H-13C correlation. Because both frequency scales, F2 and F, are lH chemical-shift scales, we can observe the transfer of coherence from Ha to Hb as a crosspeak at F = 2a, F2 = b (Fig. 9.18, lower right), as well as the opposite sense of transfer from Hb to Ha, a symmetrically disposed crosspeak at F = 2b, F2 = 2a (upper left crosspeak). In HETCOR we observe 13C coherence (in F2) that was transferred from the attached proton, whose chemical shift appears in F. Transfer in the opposite sense (13C to H) is not possible... 

Mixing Transfer magnetization from spin I to spin S. This is the only part that is different for different 2D experiments. Transfer may be by transfer of z magnetization (NOE) or by transfer of coherence (J coupling). 

Consider the transfer of coherence between two eigenoperators of the Hamiltonian (Levitt et al., 1985 Ernst et al., 1987) with... 

For the qualitative and quantitative determination of coupling constants, Hartmann-Hahn transfer can be of assistance and also provides a number of new approaches. These approaches are based on Hartmann-Hahn transfer functions or on the efficient transfer of coherence in one subset of the spin system while the polarization of a second subset of spins remains untouched (E.COSY principle). Furthermore, in combination with other experiments, the in-phase multiplets of Hartmann-Hahn experiments can be used as a reference in an iterative fitting of coupling constants in antiphase multiplets. 

With reference to the description of dipolar recoupling in the previous sections and our first presentation of these data in Ref. 70, we here demonstrate the applicability of optimal control theory for the design of dipolar recoupling experiments for transfer of coherence from N to which could involve typical and spin... 

Additional features arise from spontaneous transfers of coherence particularly, but not exclusively, when the population relaxations are very fast. The coherence equations, which are effectively the Redfield relations without interchanges of population with coherence, must be solved during each time interval and probabilities worked out for the appearance of coherences other than those that are driven by the excitation pulses. This procedure is particularly important for vibrational systems, where there are often a significant number of transitions having nearly the same frequency. For example, the coherence pj,. oscillates... 

For systems with three or more states, Redfield [19] also derived terms of the relaxation matrix for transfer of coherence between two pairs of states. These terms allow one off-diagonal density matrix element (pji ) to increase at the expense of another (pw )- Again, these terms are most important if cojk q) . 

Jeschke G, Schweiger A. 1996. Generation and transfer of coherence in electron-nuclear spin systems by non-ideal microwave pulses. Mol Phys 88 355-383. 

In the relayed coherence transfer experiment the first step is an initial homonuclear magnetization transfer (i.e., from proton A to proton B). The coherence is then relayed to a third nucleus, which may be a proton (homonuclear relay) or a different nucleus (e.g., heteronuclear relay). Recently, another variation of the relay experiment has been reported which involves transfer of coherence to a heteronuclear spin as the first step ( H-X heteronuclear shift correlation). The coherence is then relayed to a third nucleus, a proton (X- H coherence transfer), which is the nucleus observed. ... 

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