The Basics of nmr chapter 1 introduction



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Glossary


Artifact

A feature which appears in an NMR spectrum of a molecule which should not be present based on the chemical structure and pulse sequence used. [Chapter 7]

Chemical Screening

The screening of an applied magnetic field experienced by a nucleus due to the electron cloud around an atom or molecule. [Chapter 4]

Chemical Shift

A variation in the resonance frequency of a nuclear spin due to the chemical environment around the nucleus. Chemical shift is reported in ppm. [Chapter 4]

Coil


One or more loops of a conductor used to create a magnetic field. In NMR, the term generally refers to the radiofrequency coil. [Chapter 7]

Convolution

A mathematical operation between two functions. [Chapter 2]

Complex Data

Numerical data with a real and an imaginary component. [Chapter 2]

Continuous Wave (CW)

A form of spectroscopy in which a constant amplitude electromagnetic wave is applied. [Chapter 3]

Coordinate Transformation

A change in the axes used to represent some spatial quantity. [Chapter 2]

Cryopumping

The condensation of air onto a surface cooled by a cryogenic liquid . [Chapter 8]

Dephasing Gradient

A magnetic field gradient used to dephase transverse magnetization. [Chapter 11]

Digital Filtering

A feature found on may newer spectrometers which eliminates wraparound artifacts by filtering out the higher frequency components in the time domain spectrum. [Chapter 7]

Doubly balanced mixer

An electrical device, often referred to as a product detector, which is used in NMR to convert signals from the laboratory frame of reference to the rotating frame of reference. [Chapter 7]

Echo


A form of magnetic resonance signal from the refocusing of transverse magnetization. [Chapter 6]

Echo Time ( TE )

The time between the 90 degree pulse and the maximum in the echo in a spin-echo sequence. [Chapter 6]

Exchange, Chemical

The interchange of chemically equivalent components on a molecule. [Chapter 3]

Exchange, Spin

The interchange of spin state between two nuclei. [Chapter 3]

Figure-8 Coil

A magnetic field gradient coil shaped like the number eight. [Chapter 7]

Free induction decay ( FID )

A form of magnetic resonance signal from the decay of transverse magnetization. [Chapter 4]

Fourier transform ( FT )

A mathematical technique capable of converting a time domain signal to a frequency domain signal and vice versa. [Chapter 5]

Gradient ( G )

A variation in some quantity with respect to another. In the context of NMR, a magnetic field gradient is a variation in the magnetic field with respect to distance. [Chapter 7]

Gyromagnetic Ratio

The ratio of the resonance frequency to the magnetic field strength for a given nucleus. [Chapter 3]

Imaginary Component

The component of a signal perpendicular to the real signal. [Chapter 5]

Imaging Sequence

A specific set of RF pulses and magnetic field gradients used to produce an image. [Chapter 11]

Inversion Recovery Sequence

A pulse sequence producing signals which represent the longitudinal magnetization present after the application of a 180o inversion RF pulse. [Chapter 6

Inversion Time (TI)

The time between the inversion pulse and the sampling pulse(s) in an inversion recovery sequence. [Chapter 6]

K-Space


That image space represented by the time and phase raw data. The Fourier transform of k-space is the magnetic resonance image. [Chapter 5]

Larmor frequency

The resonance frequency of a spin in a magnetic field. The rate of precession of a spin packet in a magnetic field. The frequency which will cause a transition between the two spin energy levels of a nucleus. [Chapter 3]

Longitudinal Magnetization

The Z component of magnetization. [Chapter 3]

Lorentzian Lineshape

A function obtained from the Fourier transform of an exponential function. [Chapter 5]

Magnitude

The length of a magnetization vector. In NMR, the square root of the sum of the squares of the Mx and My components, i.e. the magnitude of the transverse magnetization. [Chapter 2]

Magnetic Resonance Imaging (MRI)

An imaging technique based on the principles of NMR. [Chapter 11]

Negative Frequency Artifact

The appearance of smaller in amplitude peaks in one half of the spectrum which are the mirror image of ones in the opposite half. [Chapter 8]

Net Magnetization Vector

A vector representing the sum of the magnetization from a spin system. [Chapter 3]

Nuclear Magnetic Resonance (NMR)

A spectroscopic technique used by scientists to elucidate chemical structure and molecular dynamics. [Chapter 1]

Pixel


Picture element. [Chapter 1]

Precess


A rotational motion of a vector about the axis of a coordinate system where the polar angle is fixed and the azmuthal angle changes steadily. [Chapter 3]

Proportionality Constant

A constant used to convert one set of units to another. [Chapter 8]

Pulse Sequence

A series of RF pulses and/or magnetic field gradients applied to a spin system to produce a signal whose behavior gives information about some property of the spin system. [Chapter 4]

Quadrature Detection

Detection of Mx and My simultaneously as a function of time. [Chapter 9]

Radio Frequency

A frequency band in the electromagnetic spectrum with frequencies in the millons of cycles per second. [Chapter 3]

Raw data

The Mx and My data as a function of time and/or other parameters in an NMR pulse sequence. This is also called k-space data. [Chapter 10]

Real


The component of a signal perpendicular to the imaginary signal. [Chapter 2]

Repetition Time

The time between repetitions of the basic sequence in a pulse sequence. [Chapter 6]

Resonance

An exchange of energy between two systems at a specific frequency. [Chapter 3]

RF Coil


An inductor-capacitor resonant circuit used to set up B1 magnetic fields in the sample and to detect the signal from the sample. [Chapter 7]

RF Pulse

A short burst of RF energy which has a specific shape.

Rotation Matrix

A matrix used to describe the rotation of a vector. [Chapter 3]

Sample Probe

That portion of the NMR spectrometer containing the RF coils and into which the sample is placed. [Chapter 7]

Saddle Coil

A coil geometry which has two loops of a conductor wrapped around opposite sides of a cylinder. [RF: Chapter 7]

Spin


A fundamental property of matter responsible for NMR and MRI. [Chapter 3]

Spin Density

The concentration of spins. [Chapter 6]

Spin-Echo

An NMR sequence whose signal is an echo resulting from the refocusing of magnetization after the application of 90o and 180o RF pulses. [Chapter 6]

Spin-Lattice Relaxation

The return of the longitudinal magnitization to its equilibrium value along the +Z axis. [Chapter 3]

Spin-Lattice Relaxation Time ( T1 )

The time to reduce the difference between the longitudinal magnitization and its equilibrium value by a factor of e. [Chapter 3]

Spin Packet

A group of spins experiencing the same magnetic field. [Chapter 3]

Spin-Spin Relaxation

The return of the transverse magnitization to its equilibrium value (zero). [Chapter 3]

Spin-Spin Relaxation Time

The time to reduce the transverse magnetization by a factor of e. [Chapter 3]

Sinc Pulse

An RF pulse shaped like Sin(x)/x. [Chapter 5]

Superconduct

To have no resistance. A perfect superconductor can carry an electrical current without losses. [Chapter 7]

T2*

Pronounced T-2-star. The spin-spin relaxation time composed of contributions from molecular interactions and inhomogeneities in the magnetic field. [Chapter 3]

Timing Diagram

A multiaxis plot of some aspects of a pulse sequence as a function of time. [Chapter 6]

Transverse magnetization



The XY component of the net magnetization. [Chapter 3]


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