(1) The spin of the nucleus I = 1 and thus mI = -1, 0, 1.
* If the hyperfine splitting occurs because of magnetic interaction, we can deduce that gI>0 because E(m=+1)<E(m=0)<E(m=-1). gI>0 means that the nuclear magnetic moment mu and the nuclear spin I are pointing in the same direction.
* It is not possible that the hyperfine splitting occurs due to electric interaction, because even in the case of eta != 0 (where the +/- 1 degeneracy is lifted), the m = 0 level would have the lowest energy which conflicts with energy scheme drawn here.
(2) Most nuclei will be in the lowest-energy state. In this case this is the mI = +1 state which corresponds to the I vector along the positive z-axis. This results in a polarized (pear) shape with the ‘heaviest’ part along the positive z-axis.