Factors affecting the width of the mri line
- mri experiment
I. Mri rationale
Inspired by a strong magnetic field, some atoms with some magnetic properties can crack into two or more energy levels. If, at this time, one energy is added, which corresponds to the difference between two energy levels in the immediate vicinity of the fracture, the core may absorb energy (known as resonance absorption) from low to high energy。
Mri absorption
As you know, the energy of electrons in hydrogen atoms cannot change continuously, but only takes discrete values. It is common for physical volumes to take only discrete values in the microworld. The amount of atomic nuclei that is involved in this experiment cannot change continuously, but only takes a discrete value
, where i is referred to as the spin-off quantum number, only 0,1,2,3 ... Or 1/2, 3/2, 5/2, ... Semi-integer. In
And h for planck constant. For different nuclides, i has different determinations. The spin quantum i for both protons and fluorine 19f covered by this experiment is equal to 1/2. Similarly, the self-rotation of the atomic nucleus in a certain direction of space, e. G., in the z direction, cannot change continuously, except by taking discrete values
, where the number of quantum m can only take i, i-1,...,-i +1,-i total (2i + 1)。
The nuclear nuclear atoms with a non-zero permutation are associated with a nuclear magnetic rectangle known as the nuclear magnetic rectangle. Its size is
Of these, e is the charge of the proton, m is the mass of the proton and g is a factor determined by the atomic nuclear structure. For different types of atomic core, the value of g is different and is called the g factor of the atomic core. It is worth noting that g may be positive or negative. Therefore, the direction of the nuclear magnetic rectangular may be the same as or the opposite of the direction of the nuclear voltage。
Since the nucleotide drive in any given z direction can only take 2i+1 discrete values, the nuclear magnetic rectangular may take 2i+1 discrete values in the z direction:
The magnetic rectangles of the core are usually used
As a unit
It's called a nuclear magnet. Adopt
As a unit of nuclear magnetic rectangles
Remarkable
I don't know. The size of the angular momentum itself is
Correspond, the size of the nuclear magnetic rectangular itself is
I don't know. In addition to the magnetic properties of the g-factors, another physical mass gamma, which can be measured by experiments, is usually introduced, defined as the ratio of magnetic rectangular to voltage of the atomic core:
Gamma = μ/p = g/2m
