Re: [Phys-l] spectra from flame tests

[John Denker <jsd@av8n.com>]

On 01/18/2011 04:22 PM, Brian Blais wrote:

> I was wondering if anyone has tried to observe the spectra from
> classic intro-chem flame tests.  I tried this morning, with just a
> simple diffraction grating and, for example, some sodium chloride
> salt (which glows nicely yellow for the sodium) but was unable to
> observe any of the sodium spectral lines at all: the yellow was just
> one big smudge.  I thought that either 1) I was missing some more
> careful method to observe it or 2) that, because of the complexity of
> the system (sodium, chlorine, methane in the bunsen burner,
> oxidation, etc...) that the narrow spectra lines get washed out in
> the interactions.
>
> Anyone ever do it, or, know of a more concrete reason it *won't*

Well, it certainly can be made to work:
  http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/sodium.html

Keep in mind that the fine structure splits the D line by only
one tenth of a percent, so you will need a spectrometer with
a bit of resolving power.  If your lump of sodium subtends
more than 1 milliradian as seen by the diffraction grating,
you will have to improve the geometry ... or use a more
sophisticated architecture, with condenser lenses, slits,
et cetera ... or use an out-and-out spectrometer or 
interferometer.