From: Winfield Hill
Subject: transmission of infrared through water
Date: 6 Dec 2002 06:09:58 -0800
Organization: Rowland Institute
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Bill Sloman wrote...
> Tony Williams wrote
>> Winfield Hill wrote:
>>> Tony Williams wrote...
>>>> Wavelength drift can be pure hell if the IR is going
>>>> through water, because water has a series of deep
>>>> (steep-sided) attenuation notches.... smack bang in
>>>> the 850nm to 950nm region. Been there. :-(((((
>>> Tony, kindly point us to some plots, if you can.
>> I last saw the graph in 1982 Win, after weeks of
>> struggling to find out why my water turbidity
>> meter was so unstable. But yes, it was a graph
>> of optical transmission through water, versus
>> frquency, over the range of about 800-1200nm,
>> showing a series of attenuation notches.
>> I have posted something about this before, and
>> Bill Sloman muttered something about the effect
>> being caused by hydroxyl ions (or something).
>> I'll cc this post to Bill to see if he can come
>> up with an authoritive reference.
> When I was seriously into the infra-red absorption spectra
> of inorganic compounds - back in 1964-5 - the authoratitive
> reference was Nakamoto. Amazon seems to have a much later
> edition - at vast expense - as
> Infrared and Raman Spectra of Inorganic and Coordination
> Compounds (2 Volume Set) by Kazuo Nakamoto. John Wiley;
> ISBN: 0471194069; 5th Rev up edition (August 1997).
> In any good university library nearby - MIT and Harvard
> should qualify for Win.
> The wavelengths in question are hydrogen-oxygen stretches,
> but I wouldn't have expected to see any fine structure in
> liquid water. The fine structure I was taught about was
> due to the coupling between the rotational modes of the
> water molecule (at microwave frequencies) and the stretching
> modes you are looking at at around a micron, and I'd have
> expected that to be smeared out in a condensed phase.
Thanks Tony, Bill. I'll check out Nakamoto.
Poking around on the web I found a few bits and pieces,
here's a short intro to IR spectroscopy,
This document has some interesting water-vapor curves,
A NASA document with water vapor curves, plus curves for
two types of clouds, snow, vegetation, etc.,