Illustrated Glossary of Organic Chemistry

Nuclear spin flip: Change in orientation of the nuclear spin axis upon energy absorption (excitation) or energy release (relaxation).

Orientation of
applied magnetic
field (B0)

Add energy

Release energy

I = + 1/2
Lowest energy
Ground state

I = - 1/2
Higher energy
Excited state
Change in orientation of nuclear spin upon excitation or relaxation. The arrow through each nucleus indicates the nuclear spin axis (i.e., orientation of magnetic north pole created by nuclear spin).