Nuclear magnetic resonance nuclei characteristics

Nuclear magnetic resonance (NMR) is a similar type of paramagnetic phenomenon. Like ESR, NMR involves the generation of a signal by the application of an external magnetic field, except that in NMR, shifts in the orientation of the nucleus, rather than of the unpaired electrons, are measured with respect to the external field (cf. Dyer 1965). The major point for our discussion, which would indicate that ESR rather than NMR would function as the modulated carrier-wave, is that unpaired electrons are characteristic of charge-transfer reactions and semiconduction, and as we have seen previously, serotonin and many of its analogs can function as power-... 

Nuclear magnetic resonance Characteristic excitations of an atomic nucleus causing it to flip," or alter, its. spin. state. 

The spectrometer is a radio receiver, and we change the frequency to tune in each nucleus at its characteristic frequency, just like the stations on your car radio. Because the resonant frequency is proportional to the external magnetic field strength, all of the resonant frequencies above would be increased by the same factor with a stronger magnetic field. The relative sensitivity is a direct result of the strength of the nuclear magnet, and the effective sensitivity is further reduced for those nuclei that occur at low natural abundance. For example, 13C at natural abundance is 5700 times less sensitive (1/(0.011 x 0.016)) than H when both factors are taken into consideration. 

Nuclear core The nucleus of an atom together with all inner-shell electrons but not valence electrons. Nuclear mognetic resonance Characteristic excitations of a magnetic atomic nucleus in an external mag-... 

Nuclear resonance is influenced in characteristic ways by the environments of the observed nuclei. However, nuclei are always surrounded by electrons and other atoms. Thus, in diamagnetic molecules the effective magnetic field at the nucleus is always smaller than the applied field 5 , i.e. the nuclei are shielded. The effect, although small, is measurable. This observation is expressed by equation 1 ... 

If the magnetic field gradient is applied for a short time period (i.e., a pulse ), as opposed to continuously during which time data are acquired, instead of imposing a time-independent modified resonance frequency on a nucleus as determined by its spatial position, the nuclear spin is given a phase offset (say fi) after application of the pulse characteristic of its spatial position when the pulse was applied. In the rotating frame of the spin system, this phase offset, (j)i is equal to yg i, where <5 is the duration of the applied gradient, Zi the position of the spin. 

With its natural abundance of 93.1% and a relative receptivity of its central transition comparable to that of C, K appears to be a suitable nucleus for solid state NMR. These factors are to some extent offset by its small magnetic moment and quadrupolar characteristics which have limited the number of solid-state NMR studies to date. An early study demonstrated the success of the nuclear quadrupole double resonance... 

All atomic nuclei possess a characteristic known as nuclear spin (/). However, only those nuclei with nonzero spin are NMR active, undergoing precession when placed in a static magnetic field. The unique precession frequency, known as the Larmor frequency, for each nucleus is dependent on Bq and is unique for each atom. The irradiation frequency coq applied to induce the resonance condition must match the magnetic moment s precession and is related to Bq and magneto-gyric ratio, y, of the nucleus by... 

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