Abstract
We present a calculation of the thermal mixing rate~' between nuclear Zeeman and dipolar reservoirs in the presence of large rf fields. We applied this calculation to slow-motion diffusion in lithium metal. In particular, we measured the rotating frame spin-lattice relaxation time T, p as a function of H, and observed the transition between the regions of validity of low-field and high-field theories. Furthermore, we demonstrated that this transition occurs when T, p T

If we choose the z axis to be along H", , the Hamiltonian can be written '4 ' 3Cd" =P+QĨ n the above, P =-, ' sin 8 QA".(I",I", -I"I"). . (7) @= -3 sin8 cos8 QA, , I"I". 

From conservation of energy, we see that

It is straightforward to show that (32) Tr(x*)'

Q(7) =-2isin8cos8(3cos'8 -1) ' X, ", QI", . 

Finally, Go(r) can be written in the form"

Using perturbation theory, z ' can be evaluated and is given by" ' 1, 3 cos2g -1

Go(c)= -

G"". ,

), 

From Eqs. (27) and (35), we obtain x sin'8 J~(2yH, «),

where (a&0')« is the Van Vleck second moment given by QP Jo((u) =« 3cos'8 -1 (t).&u )z 3cos28 -1

where (46) and (47) with the initial condition, P~(0)» Pd (0), we obtain

where T» is the dipolar relaxation time, the limiting case of Ty p for H, = 0.

For large H"we must consider the relaxation of the Zeeman and dipolar parts separately, as can be seen from Eq. (17). In the absence of spin-lattice relaxation, Eqs. (20) and (21) give, for H, on reso-

P z(t) = P (0) e xp(-t /, p ",, -) . 

{'paper_id': '16016067', 'title': 'Nuclear magnetic resonance in lithium metal: Thermal mixing', 's2_url': 'https://api.semanticscholar.org/CorpusID:16016067', 'source': 'S2ORC'}