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Old Oct 11th 2018, 10:25 AM   #1
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Smile Internal energy level configuration of cerium

hi, I am a graduate student in my third (research) semester. I am reading an article for four days but not getting this diagram. Can anyone explain this diagram for me?
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Internal energy level configuration of cerium ion doped into a lanthanum fluoride-capture.png  

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Old Oct 12th 2018, 02:31 AM   #2
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The left-hand panel (a) looks like an absorbance spectrum. It is a curve displaying the absorption of photons as a function of frequency. As the frequency changes, the rate of absorption changes. In QM, only photons with certain frequencies will be absorbed by orbital electrons. The consequence of this is that spikes will appear in the curve which correspond to particular orbital electron transitions and the energy of the electron transition can be calculated using E=hf, hence the author pointing out the particular frequencies of bumps in the curve.

The right-hand panel (b) is an electron energy level chart showing a schematic representation of the energy levels of orbital electrons in the ion. The ground state is usually the lowest line in the diagram and energy levels at higher energies than the ground state appear as horizontal lines further up. Possible electron transitions can then be displayed as vertical lines or arrows between the horizontal lines. Sometimes you might find some indication of uncertainty or fine structure in the form of bands; for a given level, there will be two lines either describing an upper or lower limit or a upper/lower splitting. For the specific case of this chart, the 5d state is actually five energy states with similar energies, so the right-hand part of that chart is a bit like a 'zoom-in' to more accurately display those separate energy levels. There is also an additional "Stokes shift" level, but I don't know what that is. Maybe it's explained in the text?

The two figures can be compared.

Last edited by benit13; Oct 12th 2018 at 02:51 AM.
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Old Oct 12th 2018, 09:29 AM   #3
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as this diagram is for absorbance but the internal energy diagram also has an arrow which directs to downward, which shows emissions. Can both absorbance and emission happen at the same time in a single material?
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Old Oct 15th 2018, 02:30 AM   #4
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Originally Posted by samia View Post
as this diagram is for absorbance but the internal energy diagram also has an arrow which directs to downward, which shows emissions. Can both absorbance and emission happen at the same time in a single material?
Yes.

When an electron absorbs a photon with the correct energy, it can transition from a lower level to a higher level. When in the new level, the electron is said to be in an excited state. It is possible for an electron in an excited state to spontaneously drop to a lower level, emitting a photon in the process. The absorption energy is the same as the emitted energy, so the only difference is which way the transition went.

For a substance that is having radiation shone on it, it can absorb and re-emit new photons at the same time (depending on the energy). However, a single electron is not simultaneously absorbing and emitting... it will be alternating between emission and absorption.

To get a full picture of what is happening, you need to be look at the experimental set-up and measuring apparatus to determine what is happening.

If the aim is to try and find all of the energy levels in a given range, then typically some light source with multiple frequency radiation (i.e. white light) is shone on the substance. Then, you'll measure the resulting distribution at the other side of the substance using a spectrometer. Since the re-emission of light tends to occur in different directions (perhaps even isoptropically), you'll typically find much stronger absorption spectra because the emitted light is all over the place, not just on the spectrometer.
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Old Oct 15th 2018, 09:16 AM   #5
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Smile

I got it.
Thank you
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cerium, configuration, doped, energy, fluoride, internal, ion, lanthanum, level



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