Nuclear quadrupole moment units

For quadrupolar nuclei, rapid pulsing can improve the signal-to-noise ratio. They are often most readily measured by vidde-line techniques however, as for example (84) and N (79). Many more wide-line measurements have been made of N, which is quadrupolar, than high-resolution measurements of N, which has spin but is expensive. The broadening increases with the nuclear quadrupole moment, which is small for (2.8 x 10 ), Li (4.6 x 10 ), and (—4 x 10 ), and fairly small, between 10 and 10 , for Be, B, N, S, C1, and C1 (the units are e x 10 cm, where e is the electronic charge) (20, 70). The broadening increases with asymmetry of the nuclear environment thus, the line width increases a thousand-fold from the relatively sharp line... 

The expressions for the various parts of the Hamiltonian (equation 1) are well documented and for our purpose and the following discussion it suffices to summarize the results for axially symmetric situations in angular frequency units with the equations 2-6, where and Ashielding tensor and the shielding anisotropy, respectively, D is the dipole coupling, eq or V is the electric field gradient at the nucleus, eQ is the nuclear quadrupole moment and the other symbols have their usual meaning ... 

Q Nuclear quadrupole moment in units of femtometers squared (1 fm = 10 barn). Because the determination of quadrupole moments requires knowledge of the electron configuration... 

The quadrupole moment tensor of the nuclear charge distribution is characterized by one term, that is, Q3 3, since Qu = Q i i = - Q3<3 [144], Then, the quadrupole moment, Q, of a nuclear state, in units of area, that is, barns (1 barn = 10 28 m2), is expressed as follows [143]... 

Molecular dipole moments are often expressed in the non-SI unit debye, where D 3.335 64 x 10"30 C m. The SI unit C m is inconvenient for expressing molecular dipole moments, which results in the continued use of the deprecated debye (D). A convenient alternative is to use the atomic unit, ea0. Another way of expressing dipole moments is to quote the electric dipole lengths, lp = p/e, analogous to the way the nuclear quadrupole areas are quoted (see pp.21 and 98). This gives the distance between two elementary charges of the equivalent dipole and conveys a clear picture in relation to molecular dimensions. 

Nuclei Natural abundance % Larmour frequency MHz (at 10 Gauss) Magnetic moment (in nuclear magnetons) Spin (in h units) Electric quadrupole moment (10 cm )... 

Numerical factors that can be used to obtain the value of eQV in mm or in MHz units from the value of V . In the case of 3/2 —> 1/2 transitions ( Fe, Sn, Te) the conversion factors are calculated with Q referring to the quadrupole moment of the excited nuclear state. For the other nuclides, Q refers to the quadrupole moment of the ground state. The precision of the given numerical factors is limited by the uncertainty of the respective Q values... 

The components of the g tensor of the rotational magnetic moment gga =-0.213 0.005, gbb = -0.058 0.002, gcc = -0.068 0.002, In units of the nuclear magneton, were obtained from the first-order rotational Zeeman effect. The sign was chosen by consideration of the two resulting sets of molecular quadrupole moments (g>0 Implies Q to be unreasonably large) [1,3, 26, 27] see also the tables of magnetic constants of asymmetric top molecules [4]. 

As outlined in section 1.3.2., the nuclear quadrupole interaction is characterized by two parameters, the coupling constant eQVz expressed in suitable energy units, and an asymmetry parameter tj indicating the degree of departure of the electric field gradient (efg) tensor Fy from axial symmetry. Information relevant to the lanthanide-containing metal, alloys, or compound is contained in these two parameters, since from the standpoint of the physics or chemistry of solids the quadrupole moment Q is taken to be a known property of the nuclear state. 

The table lists the element and atomic mass in the first two columns. The nuclear spin (I) is in column 3. The magnetic dipole moment /i) in units of nuclear magnetons is in column 4. The spectroscopic electric quadrupole moment (Q) in units of barns is in column 5. 

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