This is a constant representing the neutron's g factor, the characteristic proportionality constant that relates the neutron's magnetic moment, `mu_n`, to the neutron's angular momentum quantum number using the fundamental quantum unit of magnetism.

Notes

The g-factor,  `g_mu`, (also the dimensionless magnetic moment) characterizes the magnetic moment and gyromagnetic ratio of a particle or nucleus.

This constant is specified with a standard uncertainty (standard deviation) of: 0.000 000 90