By observing the transient recovery of microwave paramagnetic resonance signals at p«9.3 kMc/sec and p«34 kMc/sec, we measure the spin-lattice relaxation rate Tr 1 for the rare earth ions Nd, Pr, and Sm in the double nitrate [La 2 Mg3(N03)i2-24H 2 0] and for Ce and Nd in the ethyl sulfate CLa(C2H 6 S04)s-9H 2 OJ in the temperature range 1.4°=9.3 kMc/sec we measure Ti~l-I.7r+3.6X10~4T 9 sec -1 , as compared to the theoretical estimate, 2Y-1 = 1.4r+1.3XMW sec" 1 . The data, together with similar measurements by others, lead to the over-all * Research supported in part by the U. S. Atomic Energy Commission and the Office of Naval Research.t Based on part of the Ph.D. dissertation of P. L. Scott,
The lower energy levels of a number of transitions due to second-, third-, and fourth-nearest-neighbor chromium ion pairs in ruby are located by measuring the temperature dependence of optical absorption. Energy-level diagrams are constructed, from which many of the observed lines are identified. The measurements are consistent with earlier results for the ground states of first-, third-, and fourth-nearest-neighbor pairs. The ground-state levels of the second-nearest-neighbor pairs are describable by the isotropic exchange interaction E=J^y%% +i2(Si-S2) 2 with 72=83.6 cm" 1 and j%= -9.7 cm" 1 , where S\ and S% are the total spins of each of the two chromium ions. Description of the optically excited states requires a more general expression for the exchange interaction, of the form E-£ /#SirS2y, where su and S23 are the spins of electrons occupying the various one-electron orbitals on ions 1 and 2. The ground-state coupling parameters for the first four nearest-neighbor types are used to estimate the Ne'e! and Curie-Weiss temperatures for Cr203.
A case of classical Page kidney with emphasis on radiographic findings is presented. Onset of hypertension following trauma associated with angiographic findings of attenuation, splaying and stretching of the intrarenal vessels on the arterial phase with a definite delay in transit time through the parenchyma and a non-homogeneous nephrogram should make the diagnosis of Page kidney or constricting subcapsular mass the most logical consideration.
A regular hydromagnetic oscillation was excited in a linear discharge tube with metal walls. An externally applied axial magnetic field and discharge currents less than 104 amperes were essential to the production of the oscillation. Complete spatial current distributions derived from measurements of the radial and time dependence of the three components of magnetic field showed a helical notch (screw thread) of reduced current density which rotated with uniform angular velocity. The pitch and apparent rotational frequency of the oscillation depended on the gas density, discharge current, and applied axial magnetic field; the right- or left-handedness and rotational sense depended on the relative orientation of the applied axial magnetic field and the self field of the discharge current. The helical regularity could be described as a superposition of hydromagnetic waves traveling in the axial and circumferential directions.
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