It uses various methods to stimulate and measure luminescence.It includes techniques such as optically stimulated luminescence (OSL), infrared stimulated luminescence (IRSL), and thermoluminescence dating (TL).These slowly decay over time and the ionizing radiation they produce is absorbed by mineral grains in the sediments such as quartz and potassium feldspar.
The trapped electrons form para-magnetic centers and give rise to certain signals that can be detected under an ESR spectrometry.
The amount of trapped electrons corresponds to the magnitude of the ESR signal.
Because these can be calibrated reliably over a period of 40 million years this provides an alternate verification to radiometric dating in cases where sufficient record exists to provide a reliable trace.
Polarity reversals in the Earth's magnetic field have also been used to determine geologic time.
After a short time, electrons eventually recombine with the positively charged holes left in the valence band.