Is absolute count of emission spectrum meaningful?

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Discussion Overview

The discussion revolves around the significance of absolute counts in emission spectra obtained from photoluminescence spectroscopy of polymers using a Renishaw confocal Raman microscope. Participants explore the variability of intensity measurements and their implications for determining polymer concentration.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant notes that despite fixing laser power and exposure time, the absolute intensity counts vary for the same sample, raising questions about their reliability as a measure of concentration.
  • Another participant suggests that statistical fluctuations could account for some of the observed variability in intensity measurements.
  • A participant reports that the intensity can change by about 100%, even when measuring a consistent sample like plain silicon, indicating potential inconsistencies in the measurement process.
  • One participant emphasizes that something must be changing in the setup or measurement conditions, although the specifics are unclear without further details.

Areas of Agreement / Disagreement

Participants generally agree that variability exists in the intensity measurements, but there is no consensus on the cause of this variability or its implications for measuring concentration.

Contextual Notes

Participants mention statistical fluctuations and potential changes in measurement conditions, but do not specify the exact nature of these changes or their impact on the results.

Yinxiao Li
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I am using Renishaw confocal Raman microscope to do photoluminescence spectroscopy of some polymer inside microchannel. When I fix the laser power and exposure time, the absolute count of intensity will change from time to time even for the same sample. I was hoping the intensity should linearly reflect the concentration of polymer and why is that not the case?
(PS: I read some papers that they can use the relative intensity to tell the concentration of molecules in a solution with some other machines)
 
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Yinxiao Li said:
When I fix the laser power and exposure time, the absolute count of intensity will change from time to time even for the same sample.
How much? There are statistical fluctuations. If the difference is larger then something changes between your measurements (quite likely).
 
mfb said:
How much? There are statistical fluctuations. If the difference is larger then something changes between your measurements (quite likely).
It changes about 100%...I also used plain silicon and use f-stop to help focus on the surface. Still, the result is not consistent in terms of the absolute counts...For plain silicon, I don't think anything could change..
 
Then something changes, but it is hard to tell what without knowing the setup.
 

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