Access to eBooks is limited to institutions that have purchased or currently subscribe to the SPIE eBooks program. eBooks are not available via an individual subscription. SPIE books (print and digital) may be purchased individually on SPIE.Org.

Contact your librarian to recommend SPIE eBooks for your organization.
Chapter 6:

6.1 Absorption Parameters

The absorption coefficient α applies to irradiance (power per area), while the extinction coefficient κ applies to electric field (force per charge). The transmittance T applies to the irradiance:

T = IT/I0 = exp(−αz)

where I0 is the incident irradiance and IT is the transmitted irradiance.

The absorption coefficient α is derived from the extinction coefficient κ as

α = 4πκ/λ.

The absorption coefficient α is derived from the molar extinction coefficient αρ as

α = ραρ,

where ρ is the molar concentration. The units of molar concentration are moles per liter (mol/L). The units of molar extinction coefficient are concentration per distance [moles per liter per centimeter (mol·L-1cm-1)]. It is important to correctly define these similar metrics: absorption coefficient α, extinction coefficient κ, and molar extinction coefficient αρ.

The absorbance for a small α is defined as

A = 1−T = αz.

Online access to SPIE eBooks is limited to subscribing institutions.

Back to Top