NEQ-5 MULTI-RESONANCE SPECTROMETER

PULSED NMR MULTI-RESONANCE SPECTROMETER SYSTEM INCLUDES A CONTROL PANEL, UNIVERSAL PROBEHEAD, ELECTROMAGNET, HELMHOLTZ COILS, SAMPLES, TEXTBOOK/LAB MANUAL, ALL CONNECTOR CABLES AND PULSED NMR MODULE WITH BUILT-IN PROBE.

Study of PULSED and cw NMR Techniques. Perform ESR Experiments. Learn about NQR. Completely Computer Controlled. Upgradeable for Future Developments.

NMR - ESR

NMR and ESR are similar in concept in that both deal with the interaction of electromagnetic radiation with magnetic moments. There are two techniques for performing NMR studies: continuous wave (cw) and pulsed NMR. With the cw method the magnetic field is swept through the resonance frequency. Nuclei in the sample are selectively excited by the constant radio frequency (rf) radiation. A frequency domain absorption spectrum is obtained. In the pulsed NMR technique, the nuclei are excited by an intense pulse of rf radiation lasting only a few microseconds. When the pulse is switched off, the nuclei return to their original state emitting an NMR signal as they do so. There are three different types of measurements ("ratio", "absolute", and "relaxation time") which can be made. Within these basic groups there are several experimental possibilities. In the case of ESR, the magnetic moments arise from electrons rather than from the nuclei. As the field is swept through the resonance, electrons in the sample are selectively excited by the constant rf radiation and a frequency domain absorption spectrum is obtained.

NQR

In the case of NQR, the spectrometer detects the interaction of a nuclear quadrupole moment with the electric field gradient (EFG) produced by the charge distribution in a solid state compound. The quadrupole moments arise because the nuclear charge distribution is nonspherical. Resonance occurs when transition from one spin state to another is excited by radio frequency oscillations. In this way, NQR is quite similar in principle to NMR.

The NEQ-5 Multi-Resonance Spectrometer

It is easy to install and setup. The rear of the control panel provides a serial port for connection to the PC and clearly labeled connectors for the connecting of the various components.

Software

The software allows full control of all the spectrometer parameters such as frequency, signal gain, operational mode, amplitude, phase of carrier, modulation, time of sweep, sweep range, time constant and 1st or 2nd signal derivative. Following detection and amplification, the magnetic resonance signal is digitized in analog-to-digital converter. A trace of the signal (as function of magnetic field or time) can be observed. After signal acquisition one can zoom in on special regions of interest and correct for phase and delay. In addition, backward and forward FFT is provided. Since the software is a Windows program, printing, exporting, file saving etc. is straightforward. Windows version 3.1 or higher or Windows 95 is required.A PC based microcomputer 386 or higher with 4 MB RAM, hard drive with 5 MB available, and VGA graphics is needed.

Sample Package

Six NMR, two ESR, and two NQR samples are contained in sealed tubes for insertion into the sample cavity. The samples include: NMR: doped H ₂O, HBrF₃, PTFE (Teflon), plexi, polystyrene, and rubber + plexi.ESR: TCNQ and DPPH. NQR: NaCIO ₃, KClO ₃ . Extra sample holders are also included.

Textbook/Lab Manual

This 100 plus page monograph gives the student an understanding of the basic physical theories governing magnetic resonance phenomena. The level is suitable for those to whom magnetic spectroscopy is a new technique. Included as part of the monograph are a number of experiments illustrating concepts in (cw and pulsed) NMR, ESR, and NQR. Experiments are of two types, 1) Those dealing with instrumentation and 2) experiments to learn about the "physics" of magnetic resonance. Examples of the latter are:

a) determination of the resonance value of the magnetic field,

b) measurement of the g-factor of TCNQ,

c) magnetic field calibration using proton resonance,

d) evaluation of the gyromagnetic ratio of Fluorine nucleus,

e) finding the shape and width of the NMR line,

f) measurements of spin-lattice T ₁ and spin-spin relaxation time T ₂,

g) measurement of the number of spins,

h) determination of the number of fluorine nuclei in a Teflon sample plus much more.

Pulsed NMR Multi-Resonance Spectrometer System

The Pulsed NMR Multi-Resonance Spectrometer System includes the NEQ-5 control panel, universal probehead, electromagnet, Helmholtz coils, samples, textbook/lab manual, software and pulsed NMR Module.

cw NMR Multi-Resonance Spectrometer System

The cw NMR Multi-Resonance Spectrometer System includes everything in the NEQ-5PPulsed system except the pulsed NMR Module.

Pulsed NMR Module

Highly sophisticated technology and state-of-the-art electronics such as Quadrature Phase Detection (QPD) of the NMR signal and NMR field stabilization normally found only on very expensive resonance units, have been incorporated into the pulsed NMR module. This module contains both a built-in probehead and an NMR field stabilizer which is a miniature cw NMR device with a permanently sealed reference sample. Thus the NMR phenomena itself is used to lock the electromagnet's magnetic field by keeping a reference signal at its resonance frequency in a second independent RF circuit. A very stable and controlled magnetic field is therefore possible. The software allows the user to have complete control of the pulsed NMR module, including pulse shaping, phase shifting, signal detection, data acquisition and the processing of this data. Pulsed NMR Multi-Resonance Spectrometer System has been designed so that students can learn the basic principles of both pulsed nuclear magnetic resonance and magnetic resonance tomographs (MRT). Free induction decay (FID), spin echoes, spin-spin and spin relaxation times are examples of experimental categories which can be performed with this system.

Hardware Specification

NEQ-5 demo software
NEQ-5 technical specification

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