Electron -Spin Relaxation.jpg (91496 bytes)Energy is exchanged between the electron spin in an energy state, aligned either parallel (low energy) or anti-parallel (high energy) with the magnetic field and the phonons due to crystal lattice vibrations. In a direct energy exchange the electron spin either absorbs or emits a phonon when it undergoes a transition between the parallel and anti-parallel energy state. When the electron spin population has been inverted by adiabatic fast passage the time for them to revert to their original lower energy state is determined by the number of phonons available to provide the energy for this transition. Extensive measurements have shown that when the temperature of a Phosphorous doped Silicon crystal is reduced to liquid helium temperatures the time for electron spins to remain inverted can be many seconds.

Electron-Spin Relaxation1.jpg (23944 bytes)Cavity in liq.helium..jpg (13653 bytes)