I am not asking why an intrinsic property, like spin can have more then a single value. I understand particles (electrons) can come to existence with either up or down spin. I am asking why it can change while the particle exists.
Electrons are defined in the SM as elementary particles, and its intrinsic properties include both EM charge and spin.
The electron is a subatomic particle, symbol e− or β− , whose electric charge is negative one elementary charge. Quantum mechanical properties of the electron include an intrinsic angular momentum (spin) of a half-integer value, expressed in units of the reduced Planck constant, ħ.
The EM charge of the electron is defined as -1e, and the spin as 1/2.
Electrons have an electric charge of −1.602×10^−19 coulombs, which is used as a standard unit of charge for subatomic particles, and is also called the elementary charge. The electron has an intrinsic angular momentum or spin of 1 / 2 . This property is usually stated by referring to the electron as a spin- 1 / 2 particle.
In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei. Although the direction of its spin can be changed, an elementary particle cannot be made to spin faster or slower. In addition to their other properties, all quantum mechanical particles possess an intrinsic spin (though this value may be equal to zero).
he spin transition is an example of transition between two electronic states in molecular chemistry. The ability of an electron to transit from a stable to another stable (or metastable) electronic state in a reversible and detectable fashion, makes these molecular systems appealing in the field of molecular electronics.
So basically an electron can change its spin from up to down or vica versa, thought it is an intrinsic property.
Electrons EM charge cannot change.
In science and engineering, an intrinsic property is a property of a specified subject that exists itself or within the subject.
So both EM charge and spin are intrinsic properties of electrons. Though, electrons are coming to existence with a certain EM charge and spin. Still, EM charge is unchanged as long as the electron exists, but spin can change.
I do understand that electrons can have intrinsic properties, that can have either a single value, or a set of values. I do understand that some elecrons come into existence with EM charge and spin up. Some electrons come into existence with EM charge and spin down.
What I do not understand, is, how can spin change while the electron still exists, whereas EM charge cannot, though, both are intrinsic properties.
Do we know that when an electron undergoes spin flip (spin transition), that the electron that had originally spin up is the same quantum system that after the spin transition has spin down?
Can it be that the electron before with spin up ceases to exist (vacuum fluctuation), and then another electron is coming into existence with spin down?
Why do we say that the electron that had spin up (which is an intrinsic property) is the same quantum system as the electron that has later on (after spin flip) spin down?
After the big bang, at the baryion asymmetry, some electrons came into existence with spin up and some with spin down. Do we call these the same electrons?
Is spin the only intrinsic property of the electron that can change (like helicity)?
How can an intrinsic property of an electron change (spin flip)?
Are there any intrinsic properties (of elementary particles), that do have multiple values available, but still can't change?