Quick Question about Emission Spectra

[calbiterol]

Is the emission spectrum of an element the same spectrum of light that it will emit when photons emit light after excitation? For example, is hydrogen's emission spectrum the same as the light it emits when excited (or two-step upconverted, etc)?

 

If not, how can one go about finding the emission spectra from de-excitation of an electron in an atom at the first and second energy levels (up from natural state, in other words, the first and second excitation levels)?

 

Sorry if my terminology is a bit... Off.

[5614]

I'm not quite sure what you are asking, an atom is excited when it has excess energy and it will then release a photon... if whilst it is excited another photon hits it, well that's what happens in a laser.

 

The wavelength of the photon released by an element will always be the same as the wavelength it due to the nature of the electron, it only changes when the atom bonds or reacts.

[calbiterol]

I'm basically asking, how do you determine the wavelength of the released photon.

[5614]

I've often wondered that; it is to do with the wave like behaviour of the electrons... I think they generally just find out experimentally, I don't know if there's a formula or table of some sort.

[swansont]

I'm basically asking, how do you determine the wavelength of the released photon.

 

You can diffract the light and see how much deflection there is, or look at interference with respect to some standard wavelength.

[calbiterol]

Let me rephrase that - how do you determine the wavelength without actually producing it. A chart would be wonderful. I would try google, but I don't know the terminology to use to get any result in this case.

[Klaynos]

If you know the energy levels of the electrons you can use:

 

E=hf

 

Where E is the energy of the photon (the energy "leap" of the electron"), h is Planks constant, and f is the frequency of the photon produced.

[calbiterol]

I mean for gasses other than hydrogen. And don't you mean delta E? I don't completely understand E=hf (aka E=hv) because looking at it, it would seem like the frequency would be the same no matter what gas/element it was. A little more explanation would be... helpful.

[swansont]

I mean for gasses other than hydrogen. And don't you mean delta E? I don't completely understand E=hf (aka E=hv) because looking at it, it would seem like the frequency would be the same no matter what gas/element it was. A little more explanation would be... helpful.

 

You have to model the atoms. It gets very difficult to approximate as the atom gets larger.

[calbiterol]

Well... Helium would be a start I'm doing research on it as we speak, so I'm gradually acquiring information, so...

 

There wouldn't happen to be a chart with emission spectra / optical properties, would there?

[J.C.MacSwell]

I mean for gasses other than hydrogen. And don't you mean delta E? I don't completely understand E=hf (aka E=hv) because looking at it, it would seem like the frequency would be the same no matter what gas/element it was[/b']. A little more explanation would be... helpful.

 

The different elements produce different frequencies, as each photon "package" produced must correspond exactly to an available drop in energy level for the electron/s in the atom. The available drops in energy level vary with each element.

 

This leads me to a question that I think fits well with this thread:

 

Why is the black body radiation curve so common given that the elements behave this way?

 

Also, I know this is probably obvious but when a blackbody radiation curve is redshifted or blueshifted it is still a black body radiation curve?

[calbiterol]

I hope that question isn't directed towards anyone in particular (me) because I don't even know what black body radiation is! And, after having found a useful web resource, I think I kind of understand it - I was thinking E was in terms of energy levels (principle quantum number), but now I see it is most definitely not. It's in terms of energy, via J or eV.

[swansont]

Well... Helium would be a start I'm doing research on it as we speak' date=' so I'm gradually acquiring information, so...

 

There wouldn't happen to be a chart with emission spectra / optical properties, would there?[/quote']

 

The CRC handbook typically has that kind of information. Also, I suspect there would be online resources, and spectrosopy publications.

[calbiterol]

The CRC handbook?

[swansont]

The CRC handbook?

 

The CRC Handbook of Chemistry and Physics. Most science libraries have them, as would some Physics or Chemistry students and most professors.

[calbiterol]

Can someone explain to me the way photon absorbtion rules work? Also, I am under the impression that (at least hydrogen) can only de-excite one energy level at a time. Is this correct? Can anybody give me a link with some not-too-technical expalantion of this? I tried google, but didn't get very good responses from the search engine. Thanks.

 

Calbit

[swansont]

Can someone explain to me the way photon absorbtion rules work? Also' date=' I am under the impression that (at least hydrogen) can only de-excite one energy level at a time. Is this correct? Can anybody give me a link with some not-too-technical expalantion of this? I tried google, but didn't get very good responses from the search engine. Thanks.

 

Calbit[/quote']

 

 

No, the various spectra series (Balmer, Lyman, etc.) are transitions between all the excited states and one particuar lower state.

 

The restrictions (called selection rules) stem from things like angular momentum and parity restrictions.

 

If the ground state is an S state, or l=0 (no orbital angular momentum) then you cannot absorb a photon, with 1 unit of angular momentum, and get to a D state, which has l=2. You can get to a P state (l=1) if the energy is correct.