I don't understand why -1/2 is the higher energy level and +1/2 is the

This results in a higher energy state.In summary, the conversation is about the energy levels of spin states -1/2 and +1/2 and how they are affected by the external magnetic field and magnetic moment. The question is raised as to why -1/2 has a higher energy level than +1/2. It is explained that if the fields oppose each other, the energy level is higher, similar to how a classical magnet reacts when held in the "wrong" direction. The person is seeking clarification on this concept.
  • #1
duggielanger
17
0
This question is off my forum , and I was just wondering if anybody could help.

I don't understand why -1/2 is the higher energy level and +1/2 is the lower energy level.

For spin state -1/2, if the external magentic field B0 and magnetic moment uZ oppose each other, surely the energy level will be lower?

Likewise for spin state +1/2: if the external magentic field B0 and magnetic moment uZ are parallel with each other, surely the energy level will be higher?

My main moan is that there doesn't appear to be anything in the text explaining why spin state -1/2 has a higher energy than that of +1/2...

Can anyone help?

Thanks...
 
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  • #2


If the fields oppose each other, the energy is higher. This is similar to classical magnets: If you try to hold a magnet in the "wrong" direction, it tries to turn around.
 

1. Why is -1/2 considered the higher energy level in quantum mechanics?

In quantum mechanics, the spin of an electron can have two possible values: +1/2 or -1/2. However, the convention is to assign -1/2 as the higher energy level and +1/2 as the lower energy level. This is because the spin of an electron is associated with its magnetic moment, and -1/2 spin corresponds to a larger magnetic moment, resulting in a higher energy state.

2. How does the spin of an electron affect its energy level?

The spin of an electron is a quantum mechanical property that affects its energy level. Electrons with a higher spin (+1/2) have a lower energy level, while those with a lower spin (-1/2) have a higher energy level. This is due to the relationship between spin and magnetic moment, as described in the previous answer.

3. Is the convention of -1/2 being the higher energy level consistent across all particles?

Yes, the convention of -1/2 being the higher energy level is consistent across all particles that have spin. This includes not only electrons, but also protons, neutrons, and other subatomic particles. However, the specific values of spin and energy levels may vary for different particles.

4. What is the significance of the spin of an electron in quantum mechanics?

The spin of an electron is one of its intrinsic properties, meaning it cannot be fully explained by classical physics. In quantum mechanics, the spin of an electron plays a crucial role in determining its energy level and behavior in atomic and molecular systems. It also has implications in magnetic properties and interactions between particles.

5. Can the energy level of an electron change?

Yes, the energy level of an electron can change through various processes, such as absorption or emission of photons, interactions with other particles, or changes in external magnetic fields. However, the spin of an electron remains constant unless acted upon by an external force or undergoing certain nuclear reactions.

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