Hi, I have a few questions about spectral lines.

In the Hitran database (and other database) they uses an unit on intensity that is [cm-1/( molecule × cm-2 )] How does this work? Isn't intensity usually given in the unit [Wm-2] or [Wm-2sr-1]?

What is intensity of a spectral line? I guessing it is teh absorbance you are measuring and not the intensity with a spectrometer (transition lost by quenching, collisions, ionizations etc. ? )?

I would like to plot the emission spectra. I have been told it is not the inverse of the absorption spectra? How do I do this?

I have intensity with the unit above and the wavelengths (and some other data: Einstein A-coefficient, Lower-state energy + Upper-state ‘‘global’’ and "local" quanta + Lower-state ‘‘global’’ and "local" quanta + upper and lower statistical weights).

Intensity is elated to emission not absorption as asbsotption spectra e.g. fraunhofer lines in the solar spectrum turn up as dark lines whose intensity you can' measure.

Ok, I see..

Well, I am not going to measure these lines. I want to plot a "synthetic" emission spectra using the data from the hitemp (hitran: HITRAN) database. This simulantion will then be used by another person when he does measurement with a spectrometer ( I guess so he can identify lines and compare with his data)

I am provided with following parameters..

M =

v =

R =

A =

g

E

d

V

Q

g

g00 = Statistical weight of the lower state

I am able to plot the spectra from the data that is provided by the hitran database in matlab (but then I plot the value S as the maximum value of line.. according to its definition..is it?) , but I would like to plot the the emission spectra. According to definition in the "HITRAN paper describing 1996 edition" the intensity S is the integrated area of the spectral line. (shapded area of the line).

The lines you see in a spectra is that the absorbance or the emission that you register and not the intensity? Do you see my confusion? I guess one have to try to determine the absorbance from the hitran or???

I am thinking that maybe one could use the Kirchhoffs law to plot the emission line or maybe the Beer -Lambert Law?? Does anyone have a clue?

Any help would be very much appriciated.

Unfortunately iam not familiar with the software you are using so i wont be able to help you out there.
When you actually view the spectra, the position of the line seen depends on its frequency ,and the brightness is what we refer to as the intensity. When a larger no of atoms of an element are present, the lines appear brighter and are thus related to the concentration. If absorption spectra is being viewed, the lines will get fainter with concentration as a larger no of atoms will absorb more radiation.
The kirchoff's law is related to the spectra of black body radiation, i dont know if it is applicable here.
However the beer- lambert law is used when studying loss in intensity of a spectral line due to absorption and it provides a relationship between absorption and concentration.

The intensities of certain spectral lines of glow discharge columns in hydrogen, helium and mercury vapour have been studied in a transverse magnetic field varying from 0 to 3000 G.

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