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Magnetic dipole–dipole interaction, also called dipolar coupling, refers to the direct interaction between two magnetic dipoles. Roughly speaking, the magnetic field of a dipole goes as the inverse cube of the distance, and the force of its magnetic field on another dipole goes as the first derivative of the magnetic field. It follows that ...
For a fully oriented molecule, the dipolar coupling for an 1 H-15 N amide group would be over 20 kHz, and a pair of protons separated by 5 Å would have up to ~1 kHz coupling. However the degree of alignment achieved by applying magnetic field is so low that the largest 1 H- 15 N or 1 H- 13 C dipolar couplings are <5 Hz. [ 19 ]
HRMAS is usually applied to solutions and gels where dipole-dipole interactions are insufficiently averaged by the intermediate molecular motion. HRMAS can dramatically average out residual dipolar interactions and result in spectra with linewidths similar to solution-state NMR.
Their orientation polarisation is disturbed by thermal noise (which mis-aligns the dipole vectors from the direction of the field), and the time needed for dipoles to relax is determined by the local viscosity. These two facts make dipole relaxation heavily dependent on temperature, pressure, [6] and chemical surrounding.
The dipole has a low-lying LUMO which overlaps with HOMO of the dipolarophile (indicated by red dashed lines in the diagram). A dipole of this class is referred to as a LUMO-controlled dipole or an electrophilic dipole, which includes nitrous oxide and ozone. EWGs on the dipolarophile decelerate the reaction, while EDGs accelerate the reaction.
An electric dipole transition is the dominant effect of an interaction of an electron in an atom with the electromagnetic field. Following reference, [ 1 ] consider an electron in an atom with quantum Hamiltonian H 0 {\displaystyle H_{0}} , interacting with a plane electromagnetic wave
By truncating this expansion (for example, retaining only the dipole terms, or only the dipole and quadrupole terms, or etc.), the results of the previous section are regained. In particular, truncating the expansion at the dipole term, the result is indistinguishable from the polarization density generated by a uniform dipole moment confined ...
Electric dipole spin resonance (EDSR) is the coupling of the electron spin with an oscillating electric field. Similar to the electron spin resonance (ESR) in which electrons can be excited with an electromagnetic wave with the energy given by the Zeeman effect , in EDSR the resonance can be achieved if the frequency is related to the energy ...