Proton Enhanced Nuclear Induction Spectroscopy
Encyclopedia
Proton-enhanced nuclear induction spectroscopy (PENIS) is a nuclear magnetic resonance
technique invented by Michael Gibby and Alexander Pines
while they were graduate students in the lab of Professor John S. Waugh
at the Massachusetts Institute of Technology
. It was one of the first of Pines' experiments transferring spin orientation from one atomic nucleus to another, which has been one of the running themes throughout his career as a leading pioneer in the applications of NMR to the study of non-liquid samples. The technique was patented in 1972.
In this technique, the natural polarization
of an abundant spin
(1H
, the "proton" which begins the name of the technique) is exploited to increase the polarization of a rare spin (such as 13C
) for approximately 1.89 nanoseconds
, by irradiating the sample with radio waves at the frequency which corresponds to the difference between the rotation frequencies of the two different spins.
Besides its utility for boosting signals from dilute spins, transferring spin-polarization can also be used by surface-scientists to selectively enhance the spin-polarization of molecules on a sample's surface over the spins in the bulk by transferring spin-polarization from a gas to the surface.
Due to the suggestive nature of its acronym, the proposed name for this pulse sequence was never widely accepted. This method is now commonly known as cross-polarization and is an integral part of most solid-state NMR experiments involving spin-1/2 nuclei.
Nuclear magnetic resonance
Nuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...
technique invented by Michael Gibby and Alexander Pines
Alexander Pines
Alexander Pines is the Glenn T. Seaborg Professor of Chemistry at the University of California, Berkeley, Senior Scientist in the Materials Sciences Division of the Lawrence Berkeley National Laboratory , and a member of the California Institute for Quantitative Biosciences and the Department of...
while they were graduate students in the lab of Professor John S. Waugh
John S. Waugh
John Stewart Waugh is an American chemist and Institute Professor at the Massachusetts Institute of Technology. He is known for developing average hamiltonian theory and using it to extend NMR spectroscopy, previously limited to liquids, to the solid state...
at the Massachusetts Institute of Technology
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
. It was one of the first of Pines' experiments transferring spin orientation from one atomic nucleus to another, which has been one of the running themes throughout his career as a leading pioneer in the applications of NMR to the study of non-liquid samples. The technique was patented in 1972.
In this technique, the natural polarization
Spin polarization
Spin polarization is the degree to which the spin, i.e., the intrinsic angular momentum of elementary particles, is aligned with a given direction. This property may pertain to the spin, hence to the magnetic moment, of conduction electrons in ferromagnetic metals, such as iron, giving rise to...
of an abundant spin
Spin (physics)
In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,...
(1H
Hydrogen atom
A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively-charged proton and a single negatively-charged electron bound to the nucleus by the Coulomb force...
, the "proton" which begins the name of the technique) is exploited to increase the polarization of a rare spin (such as 13C
Carbon-13
Carbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...
) for approximately 1.89 nanoseconds
Nanosecond
A nanosecond is one billionth of a second . One nanosecond is to one second as one second is to 31.7 years.The word nanosecond is formed by the prefix nano and the unit second. Its symbol is ns....
, by irradiating the sample with radio waves at the frequency which corresponds to the difference between the rotation frequencies of the two different spins.
Besides its utility for boosting signals from dilute spins, transferring spin-polarization can also be used by surface-scientists to selectively enhance the spin-polarization of molecules on a sample's surface over the spins in the bulk by transferring spin-polarization from a gas to the surface.
Due to the suggestive nature of its acronym, the proposed name for this pulse sequence was never widely accepted. This method is now commonly known as cross-polarization and is an integral part of most solid-state NMR experiments involving spin-1/2 nuclei.