local efficiency of atomization, ɛa

in flame spectrometry
The substance fraction of atomized component in the component consumed. The efficiency of atomization is measured in a given part of the flame, usually the observation space; ɛa = ɛn.χs.χv.χa. The signal is a function of the product q v ɛ a, but ɛa is also a function of q v, usually decreasing at high volume rates.
Orange Book, 2nd ed., p. 169 (https://media.iupac.org/publications/analytical_compendium/)
PAC, 1986, 58, 1737. 'Quantities and units in clinical chemistry: Nebulizer and flame properties in flame emission and absorption spectrometry (Recommendations 1986)' on page 1741 (https://doi.org/10.1351/pac198658121737)