The temperature of the atomization surface at which the analyte signal/noise (S/N) ratio reaches a value of 3 when the quantity of analyte in the atomizer is one hundred times the characteristic mass for peak high absorption.
Source:
PAC, 1992, 64, 253. 'Nomenclature, symbols, units and their usage in spectrochemical analysis - XII. Terms related to electrothermal atomization (IUPAC Recommendations 1992)' on page 257 (https://doi.org/10.1351/pac199264020253)