Pulsed Nuclear Magnetic Resonance: Spin Echoes
ثبت نشده
چکیده
This experiment explores nuclear magnetic resonance (NMR) both as a physical phenomenon concerning atomic nuclei and as a ubiquitous laboratory technique for exploring the structure of bulk substances. Using radio frequency bursts tuned to resonance, pulsed NMR perturbs a thermal spin ensemble, which behaves on average like a magnetic dipole. One immediate consequence is the ability to measure the magnetic moments of certain nuclei such as hydrogen (i.e., the proton) and flourine; the former is of particular interest to nuclear physics. In addition, the use of techniques like spin echoes lead to a myriad of pulse sequences which allow the determination of spin-lattice and spin-spin relaxation times of substances. Among the samples available in this lab are glycerin and paramagnetic ion solutions, whose viscocity and concentration strongly affect their relaxation times. Investigation of these dependences illustrate the use of pulsed NMR as a method for identifying and characterizing substances.
منابع مشابه
Pulsed NMR Spin Echoes
Pulsed nuclear magnetic resonance techniques with transverse radiofrequency pulses are used to determine the spin-lattice and spin-spin relaxation times of glycerol and Fe solutions of varying concentrations. The nuclear magnetic moments of flourine and hydrogen are found to be μH+ = (1.408± .008)× 10−26 J/T and μF− = (1.324± .007)× 10−26 J/T, respectively. A negative linear relation in log-log...
متن کاملSpin Echoes
Intense radiofrequency power in the form of pulses is applied to an ensemble of spins in a liquid placed in a large static magnetic Geld H&. The frequency of the pulsed r-f power satisGes the condition for nuclear magnetic resonance, and the pulses last for times which are short compared with the time in which the nutating macroscopic magnetic moment of the entire spin ensemble can decay. After...
متن کاملHyperpolarized Gas Polarimetry and Imaging at Low Magnetic Field
MR imaging with polarized noble gases has shown promise in both, biomedical and material’s imaging applications. Its advantage over the conventional proton MRI lies in its ability to produce high signal-to-noise ratio (SNR), high-resolution images at low magnetic field strengths. In this work: 1. We implemented and studied in detail two methods for detecting hyperpolarization levels of 129Xe an...
متن کاملTime-reversal of cross-polarization in nuclear magnetic resonance
It is demonstrated that the time evolution of the heteronuclear polarization-transfer process in a dipolar-coupled nuclear spin system can be reversed, leading to the observation of cross-polarization echoes. The cross-polarization echoes are induced by consecutive application of two pulse trains that produce effective Hamiltonians that differ only in sign. Cross-polarization echoes have been r...
متن کامل