Raman Spectroscopy Exposure Time

[phrygian]

When you are setting up a spectral acquisition with a raman microscope, what does the exposure time mean? I would expect this to mean the amount of time the sample is exposed to the laser, but it doesn't seem like that can be true if it takes around 20 minutes to acquire the spectrum with a 2 minute exposure time...

 

[Claude Bile]

The exposure time refers to the integration time for each pixel (frequency). Some Raman microscopes extend the frequency range of the measurement by rotating the grating during acquisition, which lengthens the overall time it takes to acquire the spectrum. Think of it as the spectrometer measuring the spectrum in parts.

Other functions such as cosmic ray removal can also lengthen acquisition times beyond the exposure time.

Claude.