Dimensionless electron spin vector

This relahon differs in an important way from Equation 10.14. It says that the magnetic dipole moment is proportional to the spin vector with not only a factor of e/2mc but also with an additional factor, g. (Recall at the proportionality factor for orbital angular momentum is e/2mc.) The additional factor is required because the simple picture of circulation of charge that led to Equahon 10.14 does not apply to the intrinsic spin of an electron. The measured value for the dimensionless constant for a free electron is 2.0023. 

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