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

Notes

The g-factor,  `g_d`, (also the dimensionless magnetic moment) characterizes the magnetic moment and gyromagnetic ratio of a particle or nucleus. The g-factor relates the observed magnetic moment, μ, of a particle to the angular momentum quantum number and the fundamental quantum unit of magnetism, usually the Bohr magneton or nuclear magneton.

This constant is specified with a standard uncertainty (standard deviation) of: 0.0000000072