March 18, 2024, 10:45:43 PM
Forum Rules: Read This Before Posting


Topic: Naperian absorption coefficient and spectra slope coefficient  (Read 4108 times)

0 Members and 1 Guest are viewing this topic.

Offline STM

  • Regular Member
  • ***
  • Posts: 45
  • Mole Snacks: +0/-0
please i need simple definitions of the above terms and their implications in a water sample. I have checked the internet and obtained some information but I cant find a clear-cut definition on what they are and how they can be obtained experimentally.

What are they? How can they be obtained? What information does the result give?

Thank you

Offline mjc123

  • Chemist
  • Sr. Member
  • *
  • Posts: 2049
  • Mole Snacks: +296/-12
Re: Naperian absorption coefficient and spectra slope coefficient
« Reply #1 on: June 20, 2017, 07:31:04 AM »
Did you find this paper? http://onlinelibrary.wiley.com/doi/10.4319/lo.2012.57.5.1453/pdf. It uses both terms:
"Absorbance corrected for offset was then converted to Napierian absorption coefficient, ag(λ) (m-1). The dependence of ag(λ) on λ is typically described using Eq. 1:
ag(λ) = ag0)e-S(λ-λ0)                      (1)
where λ0 < λ and S is the spectral slope coefficient in the λ0–λ-nm spectral range. Spectral slope coefficients were estimated using a linear fit of the log-linearized ag(λ) spectrum over their respective spectral range and are reported here with units of nm-1. Measurements of DOC and ag(350) were used to calculate DOC-normalized absorption coefficients (ag(350) : DOC), expressed here in units of L mol-1 cm-1."

From this I take it that Napierian absorption coefficient is the absorbance per unit length of the sample. (Napierian means using natural logs rather than log10.) Thus A = ln(I0/It) and a = A/l, where l is the path length.
Spectral slope coefficient is a measure of how the absorption coefficient changes with wavelength. In appropriate circumstances, over a relatively narrow wavelength range, it can be described by Eq. 1, i.e. it varies exponentially with wavelength.

Offline STM

  • Regular Member
  • ***
  • Posts: 45
  • Mole Snacks: +0/-0
Re: Naperian absorption coefficient and spectra slope coefficient
« Reply #2 on: June 22, 2017, 02:52:23 AM »
Thank you for response. It was highly helpful.

Sponsored Links