Magnetic-interaction constants, defining equations

The spectroscopic determination of the spin-rotation-, spin-spin-, and nuclear-shielding parameters of diamagnetic molecules compiled here requires a resolving power of the order of 1... 10 kHz. This can be achieved with the MWFT method or with molecular-beam techniques in current irse so that the reader will find several molecules in the tables below where some of the pertinent parameters have been determined. 

We emphasize here that we had introduced in Vol. 1124 a leading factor of -1 in the spin-rotation interaction Hamiltonian, see eqs (2.30a) and (2.3 la) below. The reason for this will again be outlined later in connection with eq. (2.33a). 

The hfs plus external-field Hamiltonian may be written in tensor notation as [64Tha, 70Ver, 67Hiit]  

J is the rotational angular momentum with quantum number J, 

is the expectation value of over the state Jk k, For nomenclature regarding rotational- 

Note that authors sometimes use the notation A/ instead of C for the spin-rotation tensor. It is appropriate to refer these quantities to the molecular principal-axis system (a, b, c). In this way, the tensor 

is the expectation value of7 over the state 7. For the nomenclature regarding 

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The two factors given previously may be separated experimentally by changing the orientation of the sample compared to the magnetic field B0. For a current spectral resolution of a few Hz, order parameters S (as defined in equation 15.2) as small as 10 4 may be measured, given the large value of the bare interaction constant vQ. Note that only the absolute value of S is measured. 

The third and fourth terms in this equation represent the interaction of the electronic and nuclear magnetic moments with the external magnetic field, the difference in sign arising from the difference in the conventions used in defining gj and gj as noted above. The interaction constant Bj is identically zero if 1=0 or for the nuclear charge distribution is spherically symmetric in these cases similarly Bf is also zero if J=0, -i for then the electron charge... 

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