rate of energy deposited through ionisation from a slowing energetic particle with distance travelled in matter, the energy being imparted to the material
NOTE 1 LET is normally used to describe the ionisation track caused due to the passage of an ion. LET is material dependent and is also a function of particle energy and charge. For ions involved in space radiation effects, it increases with decreasing energy (it also increases at high energies, beyond the minimum ionising energy). LET allows different ions to be considered together by simply representing the ion environment as the summation of the fluxes of all ions as functions of their LETs. This simplifies single-event upset calculation. The rate of energy loss of a particle, which also includes emitted secondary radiations, is the stopping power.
NOTE 2 LET is not equal to (but is often approximated to) particle electronic stopping power, which is the energy loss due to ionisation and excitation per unit pathlength.