how was it done???
I guess you mean absorption spectroscopy: wide-spectrum light source, a grating, and a narrow slit.
sounds like a lot of setting up.
More than a tunable laser???
Edit - viewed link, nice instrument.
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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