Ramsey diamagnetic contribution

To evaluate ot theoretically, one must use perturbation theory. Ramsey did so (see Murrell and Harget, pp. 121-123), and found that o is the sum of two terms, a positive term od (called the diamagnetic contribution, since it decreases the applied field), and a negative term op (the paramagnetic contribution). The term op involves the usual perturbation-theory sum over excited states, and therefore is difficult to calculate however, one can use a variation-perturbation approach (Section 1.10) in op calculations. For molecular protons, od exceeds op, and aH is positive. 

Analogous expressions are found for the current density induced by a nuclear magnetic dipole m/ via the Ramsey nuclear spin/electron orbit interaction [12, 13, 15, 16, 51, 52, 61-63]. The diamagnetic contribution is connected to the probability density of the unperturbed system [59], Eq. (7.9),... 

A compromise between the opposing interpretations of Pople and Mason is offered by Webb and co-workers (46). These authors conclude that it is improper to equate the diamagnetic terms used by the two authors, since in contrast to Pople s o A, Flygare s contains significant and variable nonlocal contributions and is comparable rather to the gauge-dependent term in the original Ramsey expression (29). 

Chemical shifts, as treated by Ramsey (113), are comprised of separate diamagnetic and paramagnetic contributions. The diamagnetic term was considered to arise from the response of the extranuclear electrons to the external magnetic field and had been given earlier by Lamb (65) as... 

There are several books to which one can refer for more detailed technical information but, in general, chemical shifts for heavy and/or quadrupolar nuclei are rationalized on the basis of the Ramsey expression, equation (l) 5- 8 jqj. overall shielding (cr), made up of diamagnetic (oj) and paramagnetic (paramagnetic parameter, reflects the electron density in the immediate... 

Diamagnetic and Paramagnetic Contributions The Ramsey Theory of NMR Spin-Spin Conpling Constants (4(g))... 

Ramsey theory (p. 666) diamagnetic effect (p. 668) paramagnetic effect (p. 668) coupling constant (p. 668) direct spin-spin interaction (p. 669) diamagnetic spin-orbit contribution (p. 669) paramagnetic spin-orbit (p. 670) spin-dipole contribution (p. 670)... 

The contributions to Ja, Eq. (7.46), obtained from current density terms corresponding to a given Ramsey mechanism, e.g., the diamagnetic and paramagnetic contributions from the nuclear spin/electron orbit terms, Eqs. (7.12) and (7.14), are, respectively. 

Nuclear shielding is often discussed in the terminology developed by Ramsey (2). This approach leads to the definition of a nuclear shielding parameter o, as the sum of contributions from a "diamagnetic" term and a "paramagnetic" term oP, eq. 1, in which corresponds to the free rotation of electrons... 

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