Which emission is more likely to occur or will have more intensity then? How can we justify this with selection rules? Any references and comments will be highly appreciated.
There is the famous Kasha's rule, even in Wikipedia
Exception is azulene
As for the simplest answer: when you excite a molecule/entity in the first excited electronic state it will emit from there
There is the famous Kasha's rule, even in Wikipedia
Exception is azulene
As for the simplest answer: when you excite a molecule/entity in the first excited electronic state it will emit from there
Kasha's rule is explained here: https://en.wikipedia.org/wiki/Kasha%27s_rule
Dear Brink and McDonald,
Thank you very much for your answers. Actually I was expecting such responses; based on Kasha's rule. I am aware of Kasha's rule. However, I would like to take this discussion further in a material. If two different emissions are seen with single excitation energy, isn't it fair to say they are coming from different sites (from different elements of material)? If this is true, how do we differentiate those if elements are unknown? Do we have some other ways to verify that, based on their properties(of any kind)?
It would help if you explain what exactly are you trying to do. Is it analyse an unknown mineral?
Dear Harry,
Unfortunately I know very little about purity of the sample. I should look into the constituents for sure. About material, it's alumiosilicates of potassium, sodium, and calcium (~7.7eV band gap). Impurities could be anything.
But whatever be the impurities (and emissions from them), they must be different elements if Kasha's rule to be considered, right?
Regards, Raju
Dear Alastair,
Mineral is known but elements/constituents (not all) are not known. I'm trying to understand What do two emissions (simultaneously seen) mean in Spectroscopy?
Regards,
What do you mean with two "emissions"? Did you try an excitation spectrum of the 2 "emissions"
Even simpler why do you write TWO emissions?
Raju,
Two lines will mean two elements or, less likely, one element emitting two lines.
The strength of the lines will tell you the ratio of the elements.
It remains quiet?
Did you try an excitation spectrum?
Did you excite your material in the lowest of the 2 "emission" states?
Dear Harry,
I'm sorry for my delayed response. Due to some reasons, CCD is unable to record the data. We are trying to fix it. Once it's fixed, I will record and get back to you.
Regards,
Dear Alastair, Valeriy, and Harry
Thank you very much for all your answers and suggestions. I highly appreciate your involvement here.
Regards, Raju
This is possible if the phosphor is excited at a higher energy level than the fluorescence level
For molecular metal complexes, sometimes they can show two emissions corresponding to prompt fluorescence and phosphorescence simultaneously. This is due to the relatively slow intersystem crossing (ISC) from singlet state (S1) to triplet manifold (Tn), so that the radiative decay from S1 to S0 can compete with the non-radiative ISC process. Please see the following papers for some examples:
Article Luminescent Tungsten(VI) Complexes: Photophysics and Applica...
Article Water-Soluble Luminescent Cyclometalated Gold(III) Complexes...
Article Harnessing White Light Luminescence via Tunable Singlet and ...
Pt(II) complexes may also display two emissions in some cases due to excimeric emission, which results in a white emission:
Article Robust Phosphorescent Platinum(II) Complexes Containing Tetr...
http://onlinelibrary.wiley.com/wol1/doi/10.1002/adfm.201401244/abstract
There also exist some hybrid materials that display two emission bands arising from different components of the material:
Article Metal–organic framework composites with luminescent gold(III...
It is possible, if the source is simultaneously excites both states
Dear Michail Zuev,
Spontaneous emission. Do you or do you know the sources of spontaneous emission in the optical range? In which direction is this radiation registered? How such registration is carried out? Do not you think that spontaneous emission is a fiction? The process of spontaneous emission reduces, as a rule, to thermal nonradiative relaxation Thank you. Ogluzdin
Фотолюминесценция - это излучение на разностной частоте.
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