Chemistry Stack Exchange
Chemistry Stack Exchange

Questions tagged [spectrophotometry]

A method to measure how much a chemical substance absorbs light by measuring the intensity of light as a beam of light passes through sample solution.

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Is circularly polarized light ever used to isolate particular chiralities?

Chiral molecules tend to absorb one circular polarization of light more than the other. Is this ever used to isolate a particular enantiomer?
Dan
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Are there any (simple) molecules with very different absorption and emission dipole directions?

When a single molecule absorbs or emits light, it does so perpendicular to the direction of the respective transition dipole. In principle, the directions of the dipoles for absorption and emission can be different, due to different electronic…
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How does absorption spectroscopy work?

So a beam of white-light photons passes through a gas and various photons, having exactly the same energy as the gas's molecular energy transition state deltas, get absorbed. We then get a characteristic absorption pattern. But wait a minute, don't…
adlibber
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Why Acetone does not behave like its computational values?

I am trying to simulate the excitation state of acetone. I ran TDDFT for it both in gas phase and solvated state in water (both implicit and explicit water). The experimental data say that acetone undergoes n->π* transition, which means it has a…
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Looking for a dye which emits around 680 nm

For a specific experiment, I'm looking for a dye which would emit around 680 nm. Preferably one I could buy easily commercially. Are there any databases which might give the emission spectra of specific dyes? Or any other methods to find dyes at…
Tomi
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What is the range of photon energies can be effectively used to split a diatomic molecule like hydrogen?

I saw photo-ignition of hydrogen-chlorine mixture using UV light on YouTube. Chlorine molecule bond dissociation energy is $\pu{2.51 eV}$ (bluish colour). Bromine molecule bond dissociation energy is $\pu{2 eV}$ (orange colour). Can I use any…
SRD
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Why decarbonate soda for spectroscopy experiment?

I did an experiment with a nanodrop photometer where I had to find the amount of caffeine and benzoic acid in soda. During the experiment, we were to decarbonate the soda by heating it. I've done a similar experiment before where I had to add salt…
Melanie Shebel
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Why does sunlight cause plastics to become a faded blue color?

Due to the UV absorption, I knew that the plastics can be easily affected, especially PP. But is it normal that the change is always into faded blue from white color? and Why? Because I made an experiments, but the results made me surprised. One…
Sercan
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Home science optical absorption test for approximate caffeine quantity in coffee?

I started with How can you measure the caffeine content of a liquid at home? in the cooking stackexchange, but the test strips were only qualitative (yes/no) and don't seem to exist anymore, and the part about rubbing dichloromethane on ones gums…
uhoh
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UV/Vis spectroscopy transition reference

There are mainly fundamental transitions happening during excitation and UV/Vis spectroscopy (as n- > σ* ,π->π* ,n- > π ,..). I am looking for a good reference that shows these transitions for molecules (for example shows n- > σ* for acetone , π- >…
Aug
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Reference for UV/Vis Spectroscopic Data request

I am looking for a complete reference of UV/Vis spectroscopic data for organic materials ( mostly interested in λmax ) . I have the CRC handbook but it only has data about some organic solvents in water and very limited data on dyes. Can anyone…
Aug
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Why does ethylamine have two infra-red spectra? Are both correct?

The one I have in my textbook is this: Shouldn't the first trough at $3500$ to around $3000$ mean that it's an $\ce{O—H}$ group with a $\ce{C—H}$? And then the other trough at $1700$ be a $\ce{C=O}$? Why is this ethylamine $\ce{CH3CH2NH2}$? The…
Ollie
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Beer's law: UV-Vis absorbance values exceeding 2

In classical analytical chemistry, absorbance values in Beer's law can theoretically range from 0 to infinity. As general rule of thumb neither high, nor very low absorbance are used for constructing calibration curves. The reason for avoiding high…
AChem
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How to choose the correct volumes when preparing a dilution series?

Original Question A solution of dye, Amido Black 10B dye ($10~\mathrm{mM}$, $6.165~\mathrm{g\over L}$), as-provided absorbs light much too strongly for measurement of an absorbance value. It is therefore necessary to dilute it before proceeding…
Eve
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Optional determination techniques in Atomic Absorption Spectroscopy

I have tried to find information about this case but I couldn't find anything specific. The key point of instrumental methods of analysis, is for the student to be able to know which one of the possible methods to use for a specific determination.…
Ndrina Limani
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