Timeline for What does the Interferogram of a FTIR-spectrometer show ? Is it instantenous intensity vs time or time averaged intensity vs time?
Current License: CC BY-SA 3.0
12 events
| when toggle format | what | by | license | comment | |
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| Jul 17 at 22:23 | answer | added | olesole | timeline score: 1 | |
| Sep 14, 2021 at 15:00 | history | tweeted | twitter.com/StackPhysics/status/1437793331526914065 | ||
| Sep 11, 2021 at 17:27 | comment | added | Ed V | This is very late, but I just saw your question. When I do simulation of FTIR, as here, I use an optical calculus, a set of discrete light wavenumber values (‘colors’) and the photodetector response is the summed response of each of the modulated discrete light ‘colors’. For any given moving mirror position, each ‘color’ has some degree of interference. As the mirror is stepped in fine steps, each color is modulated at a frequency proportional to its wavenumber value. I do not try to model Haidinger fringes or the like. | |
| Aug 4, 2017 at 12:23 | comment | added | Hans Wurst | The link does not specify whether the detector averages or not over the signal for a given mirror position. I know the general workings of FTIR spectroscopy, what i miss is more or less a detail how the detector works. I found many links with general explanations and some formulas but most were rather sketchy on the exact details. That is why i ask here. | |
| Aug 4, 2017 at 11:28 | comment | added | Alchimista | Might be worth a look newport.com/n/introduction-to-ftir-spectroscopy | |
| Aug 4, 2017 at 8:34 | comment | added | uhoh | Thanks for the clarification. Yes, we first learn about the intensity of a theoretically monochromatic beam of light as a simple time-average over one cycle. Then we have to un-learn that when starting down the rabbit hole where more complicated interference effects and concepts in statistical optics are studied (intensity interference, what the heck is that?). FTIR is as good a place as any to start thinking about this! | |
| Aug 4, 2017 at 8:32 | comment | added | Hans Wurst | This picture shows exactly my problem! What is ment exactly with "Light measured by detector"? Can you give formulas based on incoming electromagnetic field that is superimposed at the detector? Is it the magnitude of the poyinting vector at the detector or the time averaged poynting vector magnitude ? | |
| Aug 4, 2017 at 8:30 | comment | added | Hans Wurst | My goal is to get step by step or rather question by question to the "how does an FTIR spectrometer operate". I thought that question would be to generalized. At the moment i would like to focus on the measured interferogram that is later on fourier transformed to obtain the spectrum. The inteferograms are often shown but it is not clearly stated what the y-axis so to say exactly shows. Intensity is quite a blurry term and should be further quantified in my opinion. The word intensity is sadly often used for different physical quantities but i want preferable in formulas exactly whats measured | |
| S Aug 4, 2017 at 8:29 | history | suggested | uhoh | CC BY-SA 3.0 |
fixed several grammar issues, added a link to FTIR, and an example of an FTIR interferogram for reference.
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| Aug 4, 2017 at 8:13 | comment | added | uhoh | It's a good question in principle, but there's two questions here perhaps. 1) How does an FTIR spectrometer operate, and 2) what might average intensity and instantaneous intensity really mean in the context of experimental optical metrology? | |
| Aug 4, 2017 at 8:11 | review | Suggested edits | |||
| S Aug 4, 2017 at 8:29 | |||||
| Aug 4, 2017 at 7:02 | history | asked | Hans Wurst | CC BY-SA 3.0 |