Spectroscopy before tunable lasers?

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    Lasers Spectroscopy
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Discussion Overview

The discussion revolves around the methods and challenges of performing spectroscopy before the advent of tunable lasers, specifically focusing on absorption spectroscopy and the equipment used in earlier practices.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about the methods used for spectroscopy prior to tunable lasers.
  • Another participant suggests that absorption spectroscopy involved a wide-spectrum light source, a grating, and a narrow slit.
  • Concerns are raised about the complexity and setup time required for traditional spectroscopy compared to using tunable lasers.
  • A participant references a link to an antique instrument, expressing interest in its power spectrum and bandwidth.
  • Discussion includes the manual adjustment of diffraction gratings for frequency sweeps, with some participants noting the historical context of these methods.
  • One participant shares their experience with drift and mode hopping issues in spectroscopy, indicating challenges faced in maintaining wavelength accuracy.
  • There is speculation about the automation of tunable lasers in contemporary use, contrasting with older manual methods.
  • Questions arise regarding the bandwidth of the antique instrument mentioned in the link.

Areas of Agreement / Disagreement

Participants express varying levels of familiarity and experience with traditional spectroscopy methods, but there is no consensus on the specific challenges or advantages of these methods compared to modern tunable lasers.

Contextual Notes

Participants mention issues such as continual drift, mode hopping, and the need for manual adjustments, which may depend on specific setups and definitions of equipment.

houlahound
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how was it done?
 
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I guess you mean absorption spectroscopy: wide-spectrum light source, a grating, and a narrow slit.
 
sounds like a lot of setting up.
 
houlahound said:
sounds like a lot of setting up.
More than a tunable laser?
 
Edit - viewed link, nice instrument.
 
houlahound said:
I would like to see the power spectrum and bandwidth of a line from the source. so a frequency sweep means you change the angle of the diffraction grating - ouch.
I don't see the difficulty in that. In the old-old days, it was done manually (grating on a pivot), later using a motor.
 
I guess if I got this right due to the physical set up a particular line you select is locked there indefinitely and you just know it's that wavelength forever.

the only time I did real spectroscopy there was continual drift and I had to fix the wavelength with a beam splitter and compare to another sample of with known line. there was always mode hopping issues but that did not bother what I was doing.

I suspect tunable lasers are prolly all automated now to stay on a line. the bandwidth was very narrow, would like to know what the bandwidth is for the antique instrument in the link.
 

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