A fully homemade 14N quadrupole resonance spectrometer

A fully homemade 14 N quadrupole resonance spectrometer

A novel theory, based on density operator calculations, is provided for assessing the nuclear quadrupole resonance behaviour of a spin 1 (14N) subjected to a single radio-frequency pulse. It is for a powder sample in zero magnetic field for an electric field gradient tensor without symmetry. A complete set of equations is obtained for the quantities of interest. It is derived from the general Liouville–von Neumann equation and from a proper basis on which the density operator is expanded. Theoretical results, in terms of signal evolution as a function of the pulse length (nutation experiments), show that the same nutation curve is expected for the three different transitions which exist when the electric field gradient tensor is without symmetry. This latter nutation curve is, however, different from that which prevails in the case of an axially symmetric tensor, this apparent discrepancy being easily resolved on theoretical grounds. Experimental data (for NaNO2, electric field gradient tensor without sym...

14N Pulsed nuclear quadrupole resonance. 2. Effect of a single radio-frequency pulse in the general case

An exact theory based on density matrix calculations is provided for assessing the nuclear quadrupole resonance (NQR) behaviour of a spin 1 (14N) subjected to a single radio-frequency pulse. It concerns a powder sample in zero magnetic field with the assumption of an axially symmetric electric field gradient tensor. Theoretical results, in terms of signal evolution as a function of the pulse length (nutation experiments), are checked against values of the radio-frequency field amplitude provided by NMR measurements performed with the same equipment. Good agreement between theory and experiment is obtained.

14N pulsed nuclear quadrupole resonance. 1. Nutation experiments in the case of an axially symmetric electric field gradient tensor

Spin-echoes in nitrogen-14 quadrupolar spin-system with axially symmetric electric field gradient tensor.

The interaction representation is used to describe the pulsed response of an ensemble of spin I= 1 nuclei experiencing quadrupolar and dipolar couplings in zero applied magnetic field Particular attention is given to the case of coupling between physically inequivalent spins, the case of equivalent spins being included as a special case Axial symmetry of the electric field gradient tensor is assumed for all spins

Arthur Watton

Papers

Zero-field pulsed response and dipolar couplings in systems of spin I= 1 nuclei