symbols: $\alpha_{\lambda}^{\ast}$, $a_{\lambda}^{\ast}$; units: $\pu{m kg-1}$, $\pu{m g-1}$, $\pu{cm2 g-1 nm-1}$
synonyms: specific linear decadic spectral absorption coefficient, specific linear Napierian spectral absorption coefficient, specific spectral absorption coefficient
https://doi.org/10.1351/goldbook.14091
Linear napierian, \(\alpha_{\lambda}^{\ast}\), or linear decadic, \(a_{\lambda}^{\ast}\), absorption coefficient divided by the mass concentration, \(\rho\).
Notes:
- The asterisk as superscript indicates that it is a specific property.
- Absorption coefficient is always a spectral property; the subscript \(\lambda\) may be omitted but the wavelength should be specified.
- Mathematical definition: \[\alpha_{\lambda}^{\ast} = \frac{\alpha_{\lambda}}{\rho} \quad {\rm{or}} \quad a_{\lambda}^{\ast} = \frac{a_{\lambda}}{\rho}\] SI unit is \(\pu{m kg-1}\) , common unit is \(\pu{m g-1}\) or \(\pu{cm2 g-1 nm-1}\).
- For reacting systems with mass fluctuations and high scattering, space- and time-dependent specific, napierian and decadic, absorption coefficients are necessary, i.e., \(\alpha_{\lambda}^{\ast}(\boldsymbol{x},t)\) and \(a_{\lambda}^{\ast}(\boldsymbol{x},t)\), respectively; \(\boldsymbol{x}\) defines the position in a three-dimensional space.