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NMRS 2008 Presentation
Department of Chemistry
NORTH EASTERN HILL UNIVERSITY
SHILLONG 793022 MEGHALAYA
A STUDY ON THE FEASIBILITY OF
A SPIN PRECESSION PICTURE TO DESCRIBE NQR PHENOMENON
Department of Chemistry
North Eastern Hill University
Shillong 793022 Meghalaya
Abstract: The NMR phenomenon is describable in terms of the interaction of the vector quantities associated with the fundamental nature of the Nucleus, and, the externally applied Magnetic field which is also a vector. The NQR phenomenon is describable only in terms of the interaction due to the Tensor properties associated with the fundamental nature of the nucleus and the Electric Field Gradient which is in general a Tensor. This difference is between the two phenomena is considered from the point of view of the precession picture readily available for the description of NMR while such a simple precession picture seems elusive while describing NQR.
Approach: To describe the NQR phenomenon in a manner analogous to the precession description of the NMR, it is required to assign a fixed direction for the Spin Angular Momentum Vector of the nucleus with respect to the nuclear QM. This assignment is made by trying to specify a line and associate this line with the nuclear QM (eQ). Then, if the nuclear Spin Angular Momentum Vector of the nucleus can have a fixed angle with respect to the line associated with (eQ) (even without specifying the actual value for the angle) then, conventional direction of the largest component Vzz of the Principal Axes System of the EFG tensor would determine (similar to the direction of an external DC magnetic field for NMR) the quantization axis for the Spin Angular momentum while the QM interacts with the EFG.
Result: By an approach as described above, for the tensor nature of the interactions in NQR, an effort is made to find vector directions characteristic in such an interaction which can give a parallelism with the interactions in NMR. Once the parallelism is convincing the precession picture would follow as much readily as in the NMR case. Thus a precession description for NQR phenomenon is a possibility even though it cannot be concretized as readily as in the case of NMR. This possibility would be given a detailed consideration for an eventual introductory precession picture description for NQR as much routinely as for the NMR.
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