Spectroscopy is the study of the interactions between matter and radiated energy. Experimentally, the results are returned as a function of wavelength versus amplitude (intensity), where the spectral lines represent the resonance frequency of the sample.

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Why does Stokes raman not relax to the ground state while anti-Stokes does?

I'm just wondering why stoke-Raman doesn't go to the ground state. Where does the rest of energy from exciting laser leave? On the other hand, why does anti-stoke go back to ground state? I know that ...
4
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2answers
67 views

1H (proton) NMR spectra for alkanes

I do not fully understand the idea of coupling and why chemically equivalent hydrogens do not couple. I wanted to work with the alkanes, so let's take propane first: There would be a triplet ...
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1answer
45 views

Determination of brominated aromatics by 13C and 1H NMR spectroscopy

How can I identify 4-bromoazobenzene, 4-bromoazoxybenzene, and 4,4’-dibromo-$\ce{N,N}$’-diphenylhydrazine products using $^1\ce{H}$ and $^{13}\ce{C}$ NMR? I’m really confused by the general shape of ...
3
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1answer
44 views

Deducing compounds from spectroscopic data for isomers of formula C4H8O

Here's the problem: I've already know the 3600 cm$^{-1}$ line indicates the $\ce{-OH}$ group and the 1640 cm$^{-1}$ line indicates the C double-bond C alkene. From the $^{13}$C NMR data: the two ...
7
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52 views

What is the difference between infrared action spectroscopy and conventional IR spectroscopy?

I'm familiar with infrared spectroscopy generally, which probes mainly the vibrational behavior of molecules under study. However, I'm seeing references in various literature to 'infrared action ...
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80 views

Why are porphyrins colored when porphyrinogens are colorless?

In heme synthesis, porphyrinogens are colorless but upon their oxidation (from removing 6 hydrogen atoms), they become colored porphyrins. Why does the change in color occur? Is red the only color it ...
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1answer
23 views

Relation between number of conjugated double bonds and absorbance? [duplicate]

I observed the absorbance on Phenolphthalein in acidic and basic medium, and I know that the absorbances differ due to the number of conjugated double bonds, but I am not sure exactly why this ...
5
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57 views

A compound that only absorbs UV-A radiation

As a similar idea to the question A compound that absorbs all visible light, I am curious if there is a compound (or compounds) that absorb UV-A radiation (shown below)? However, preferable the ...
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A compound that absorbs all visible light

Is there a compound that absorbs all visible light?
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1answer
97 views

Determining Molecule Based on Proton NMR (HNMR)

Based on the NMR data, I have determined that the molecule must be 1-phenoxy-2-propanone, however I may be wrong because given the proton NMR, there are only 4 unique carbon environments, however in ...
5
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1answer
46 views

Are there any early industrial age methods capable of determining diamond or graphite's crystalline structure?

I'm writing a fictional story with early industrial age technology where a chemist discovers not only that diamond and graphite are made of the same substance, but that they differ by crystalline ...
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75 views

Why is an alcohol proton so shielded?

Considering how electronegative oxygen is, why is the chemical shift of alcohol protons (1H-NMR) not so high? The chemical shifts of the protons on 3-propanol are about 1.20 for the carbon-1 ...
7
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1answer
81 views

Calculation of fluorescence quantum yield

The fluorescence quantum yield of a sample $\Phi$ is defined as the fraction of photons emitted per number of photons absorbed. The quantum yield is often calculated by comparing a sample with a ...
3
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1answer
37 views

Relation between electric dipole moment and polarization?

Eq. 1: $\space$ $\vec{p}_\text{ind}=\alpha \vec{E} $ The induced dipole moment is the polarizability times the electric field vector. Eq. 2: $\space$ $\vec{P}(\omega) \propto \chi^{(1)}(\omega) ...
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1answer
96 views

Near IR spectroscopy vs. IR spectroscopy

I am a backer of this Kickstarter: SCiO Near IR Spectroscopy Here is a link to their technology: SCiO Technology Question: How short of full IR spectroscopy do you think this device is? I have asked ...
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1answer
29 views

What are scattering losses?

In UV spectroscopy, when a beam of light is shone into solution, what is scattering loss during this process?
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24 views

several coefficient differences in UV-vis Spectroscopy

Does anyone know what is scattering coefficient, absorption coefficient and extinction coefficient, and how to separate them experimentally?
3
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1answer
96 views

difference between absorption spectroscopy and extinction spectroscopy [duplicate]

can anyone tell me the difference between absorption spectroscopy and extinction spectroscopy in terms of experiment? and how to get extinction spectroscopy, how to get absorption spectroscopy? Thank ...
5
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1answer
52 views

Why do we say approximation in the dipole approximation in spectroscopy?

In the dipole approximation the following relation holds: $\hat{V}=-\hat{\mu}\overrightarrow{E}$. When we say "approximation" I guess we want to point out, we are dealing with linear spectroscopy, ...
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62 views

How Do I Identify What Impurities Are in My Product?

I am writing a lab report for Organic Chemistry about a multi-step synthesis that we conducted. While our product has the proper melting point, its IR spectrum has peaks not present in the respective ...
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1answer
36 views

Are there any free phosphorus-31 NMR spectral libraries?

I know that there are some sites like Sigma Aldrich and AIST for $\ce{^1H}$ NMR and $\ce{^13C}$ NMR, but was wondering if there were any free sites to compare $\ce{^31P}$ NMR spectra?
4
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56 views

In spectroscopy, is it possible for the sample to be excited multiple times?

The context of my question is rotational spectroscopy (using microwave radiation), where there is the $J = \pm 1$ selection rule. The way I understand spectroscopy is that the sample is irradiated ...
4
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2answers
390 views

Why is wavenumber used in IR spectroscopy rather than wavelength?

In IR spectroscopy, the $x$-axis is used to represent wavenumber, in $\mathrm{cm^{-1}}$. Why is wavelength, equal to $1/\lambda$, used in place of wavelength, which is simply $\lambda$? Sources I’ve ...
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1answer
28 views

IR fluorescent material for outdoor use

I am experimenting with IR video cameras. They have a broad sensitivity peak at 940 nm. There is a filter blocking 750 nm and shorter in front of the sensor. I am looking for an IR fluorescent ...
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28 views

Can one figure out an optical absorption spectrum from EPR data?

I'm wondering if it's worthwhile for me as an optical spectroscopist to read up a bit on EPR. Do EPR signals reveal where, in terms of wavelength, features in the optical spectrum can be expected to ...
4
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1answer
221 views

Bohr's model of atom

"the most remarkable success of the Bohr's theory is that it provides a satisfactory explanation for the line spectrum of hydrogen." But what is the problem with line spectrum of hydrogen which ...
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196 views

Are the bonding orbitals in methane equivalent - photoelectron spectrum

The low energy portion (the part dealing with the $\ce{2s}$ and $\ce{2p}$ electrons) of the photoelectron (PE) spectrum of methane is reproduced below. (image source) The reaction being examined ...
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63 views

Explaining the photoelecton spectrum of krypton

The photoelectron spectrum of krypton is shown below. (where the x-axis is in electron volts (eV))\ Since both the $3p$ and $3d$ shells are more than half full, based on Hund's rules the ...
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46 views

Possible ionization and fragmentation of chemicals

Is there any generic method where I can know/calculate/generate the possible ionization and fragmentation of a specific chemical, for example, hydrogen chloride and water. Replies are greatly ...
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1answer
25 views

Identifying phycobiliprotein based on wavelength

I have the absorption spectrum of a specific phycobiliprotein. Its maximum wavelength is 620.6 (nm),this is the only data I have. How can I know what type of phycobiliprotein it is?
3
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47 views

Choosing the instrumental techniques for chemical analysis [closed]

Since every technique has its goods and its bads characteristics, it's a bit hard for me to choose between them to determine specific elements, methods such as UV-VIS spectroscopy, IR spectroscopy, ...
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43 views

How photoluminescence (PL) spectroscopy works

Photoluminescence (PL) spectroscopy is used to find the energy levels in a compound but how does PL spectroscopy works? After exciting a material with a particular wavelength whether PL machine looks ...
2
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0answers
53 views

Carbonyl group Conjugation and IR spectroscopy

Here's the problem... Three isomeric structures with formula $\ce{C10H8O2}$ are shown: I understand that conjugation in the systems will affect the carbonyl stretching ...
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16 views

Qualitative spectrographic analysis

In order to identify the presence of a specific element, one must identify at least three ultimate lines of that element in the specter. Those lines are the ones with the highest intensity. I ...
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1answer
41 views

Atomic emission spectroscopy

There is a sentence in my book I don't understand : Every atom or ion, which has one valence electron, will have double lines in the atomic emission spectrum. For example $\ce{Na}$ will produce lines ...
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39 views

The relation between magnetic resonance spectroscopy and the causes and effects of electromagnetic induction

This is a more physics question, but I need specific chemical knowledge and opinion. Using electric charges to produce current, it was found that an electric charge and magnetic dipoles are related ...
3
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38 views

Has a triplett sigma state of a diatomic molecule a spin orbit coupling?

I know that states with spin S=0 in a diatomic molecule have no spin orbit coupling, independent on the value of the projection of the total electronic angular momentum. I expect the same is true if ...
2
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0answers
38 views

Relevance and Determination of the reflection symmetry +/- in Spectroscopy?

If there are two electrons located in a shell (which contains two subshells) the molecule can either have a singlet state (if both electron are in the same subshell; because of the Pauli principle) or ...
3
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2answers
159 views

How to interpret orbital transition in TDDFT?

Consider the following TDDFT run with GAMESS: ...
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2answers
194 views

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 ...
6
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1answer
75 views

Determination of mercury in AAS

Its known that the only method to determine mercury in atomic absorbtion spectroscopy is the cold vapor method. What is the reason that mercury can't be determined with other methods, such as flame, ...
2
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23 views

How to confirm the type of bonding taking place between two substances?

For example ink on paper: how can I confirm that the bonding is van der Waals and not covalent? Similarly, the same question can be asked about other interaction such as hydrogen bonding, ionic ...
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1answer
37 views

Is a microwave oven dangerous? [closed]

If we take a look at the electromagnetic specter, microwave wavelength is higher than infrared, which means its energy is very small. To break chemical bonds, the energy required is 100-1000 kJ/mol, ...
3
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0answers
24 views

Why might the ratio between two Q-band peaks in ZnTPP decrease with increasing temperature?

In ZnTPP (Zinc tetraphenylporphyrin), there are two Q-band emission peaks. When I run steady state emission measurements at different temperatures, the ratio of their respective peak intensities ...
4
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1answer
36 views

Is it possible to predict the lines in the atomic emission spectrum of Na?

The atomic emission spectrum for sodium ($\ce{Na}$) is completely dominated by a line in the range of yellow, about $590~\mathrm{nm}$ (to be more precise, it's a doublet). Here is how it looks like: ...
8
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2answers
245 views

Rotational degrees of freedom (3N-5 and 3N-6)

In spectroscopy we described the electric energy with the approximative separability of internal motions as: \begin{equation} E=E_e+E_v+E_r+E_{ns} \end{equation} (energies: electronic, vibratory, ...
7
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1answer
45 views

Wavelength extention in AAS

Theoreticly, the width of the spectral line in AAS (atomic absorbtion spectroscopy) is 10^-5, but in fact there happens an extention of it and it becomes 0.002-0.005. There are some factors which ...
6
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1answer
140 views

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 ...
2
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1answer
144 views

Auxochrome groups

Functional groups like $\ce{OH}$, $\ce{NH2}$, attached to nonsaturated compounds (chromophores) are called auxochromes. These groups tend to shift the wavelength to the infra-red area which is called ...
3
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1answer
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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 ...