absorption coefficient

1. (in spectroscopy) The molar absorption coefficient (symbol ε ) is a quantity that characterizes the absorption of light (or any other type of electromagnetic radiation) as it passes through a sample of the absorbing material. It has the dimensions of 1/{concentration x length). e is de­pendent on the frequency of the inci­dent light; its highest value occurs where the absorption is most in­tense. Since absorption bands usually spread over a range of values of the frequency v it is useful to define a quantity called the integrated ab­sorption coefficient, A, which is the integral of all the absorption coeffi­cients in the band, i.e. A= ʃε(v)dv. This quantity characterizes the inten­sity of a transition. It was formerly called the extinction coefficient

 2. The volume of a given gas, measured at standard temperature and pressure, that will dissolve in unit volume of a given liquid.