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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Amount of substance of a molecule in a solute the same as amount of substance of constituent elements?

I've done absolutely no chemistry since high school. Now, 16 years later, I've been asked to look at some chemical analyses and I'm having trouble! Context: I've got a series of spectroscopy ...
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33 views

Do core electrons in bulk material have discrete energy levels or continuous energy band?

The energy band of valence electrons gets smaller and smaller when the lattice (bulk) atoms are more and more separated from each other, until discrete energy levels are formed, due to the isolation ...
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31 views

In infrared spectroscopy, why is there no C=C reading for E alkenes?

For the (E)-2-pentene, there was no C=C reading, about 1600. For the (Z)-2-pentene, there is a C=C. Why is there a reading on the Z but not on the E?
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Finding identities of diatomics from Spectroscopy and Mass Spec Data

Let's say I have a sample of 2 (assumingly different) diatomics A and B. Through Spectroscopy I found the data below: For molecule A: $$B ̃=2.17690\space cm^{−1}$$ $$D ̃=4.79000×10^{-5} cm^{−1}$$ ...
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31 views

Lambert Beer's law deviations

Can somebody explain as concrete as possible, how the change of temperature and the change of ph leads to deviations of this law ?
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33 views

Why the magnitude of dipole moment influences on FTIR % transmittance?

In 3:50 of this video two FTIR spectras are shown. He explains that the % transmittance (double bond in his example) depends on the dipole moment, $\mu = \delta \cdot d$. I understand that the ...
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28 views

What does the peak separation of carbon dioxide IR rotational-vibrational spectrum corresponds to and why?

Spectrum of $\ce{CO2}$ at $2349\space \mathrm{cm^{-1}}$ region For some other molecules (for example $\ce{CO}$) the peak separation corresponds to $2B$ (where $B$ is the rotational constant ...
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2answers
80 views

Stern Volmer Plot and calculating rate constant for quenching kq

I did an experiment irradiating benzophenone in UV light and worked out the rate constant for the reaction. Then I repeated the experiment using various concentrations of a quencher and worked out ...
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1answer
38 views

¹H-MRS Detection of Dopamine

Why is it difficult to detect dopamine using $\ce{^1H}$ Magnetic Resonance Spectroscopy (MRS) in the brain (in vivo)?
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11 views

Which causes of quenching increase specifically in electrochemical experiments?

If quenching is seen as a result of running electrochemical experiments on a solution, what kind of processes may be responsible? I'm thinking about UV/Vis spectroscopy, if it makes any difference. ...
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49 views

How to predict the ³¹P NMR spectra?

What can I predict about the $\ce{^{31}P}$ spectra of $\ce{TiP2O7}$? To get the required information about the crystal structure of the compound, here is a screenshot from the ICSD website: Since ...
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1answer
39 views

Why do the two methylene protons in ethylbenzene have a chemical shift at 2-2.9?

The data sheet does not have any chemical shifts in this range for compounds containing only carbon and hydrogen
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99 views

Methylene blue used as funguscide in cichlid reproduction - concentration measurement?

I have an aqueous solution of methylene blue. How do I determine the concentration of this solution, so I can duplicate it?
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1answer
57 views

Why do molecules have to have a change in dipole moment in order for them to be IR active?

My chemistry textbook keeps saying that in order for a molecule to be able to absorb infrared radiation, it has to have a change in dipole moment when the bond vibrates. I don't understand why that ...
4
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2answers
76 views

Wavelength of iPhone 4S camera light for visible spectroscopy calibration

I ordered a DIY spectroscopy kit from public-lab, however don't have access to a halogen lamp to calibrate the wavelengths. I'm wondering if it would somehow be possible to calibrate the wavelength ...
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1answer
37 views

Lifetime measurement: double peak in instrument response function

I am measuring flourescence lifetimes with a picosecond pulse laser, using the LifeSpec II with an MCP detector. Instead of a single peak rapidly decaying, as would be expected, my IRF contains two ...
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1answer
60 views

How exactly are molecules detected in space?

Recently the sugar glycoaldehyde was detected in a star system 400 light years from Earth. How exactly are molecules detected in space? I am aware that spectroscopy is used to detect them, but I don't ...
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1answer
53 views

Spin spin coupling in a proton NMR of an ester?

I am learning about proton NMR and spin-spin coupling, and am confused about whether splitting occurs over an ester bond. Specifically, in the case of ethyl methanoate, HCOOCH2CH3, if I were to number ...
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1answer
64 views

Standard curve of absorption and concentration

I just wanted some quick help with a lab I'm doing, based on absorption spectroscopy. I'm given an aqueous stock solution of Yellow Dye #5 with a concentration of 54.5 micro moles. I'm asked to ...
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4answers
106 views

Could I get a hint on the structure of this molecule based on HNMR spectra?

Chemical formula is $\ce{C7H6O3}$. IR spectra has a peak at 3238, which I believe could be an alcohol, phenol, or carboxylic acid. There's an additional peak at 3015, which I believe is either an ...
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27 views

I need a good reference (book) to learn about Diffuse reflectance Spectroscopy, could you suggest at least one, preferably in pdf format?

I need to learn how to explain, interpret and extract information from Diffuse reflectance Spectroscopy, because I have the data but I do not know how to build a relation in between. Thanks for your ...
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20 views

So of the different characteristics of a XRD plot, wich is most appropiate to identify and suggested one phase among others?

This is the XRD Powder plot of a sample prepared with {La, Ti, K and O}. Thanks a lot for your suggestions. So of the different characteristics of a XRD plot, which is most appropriate and suggested ...
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2answers
80 views

Why would there be differences in UV/Vis spectrum?

$\ce{[NEt4]2[NiBr4]}$ dissolved in $\ce{MeCN}$ and $\ce{[NEt4]2[NiBr4]}$ dissolved in $\ce{H2O}$ have different UV/visible spectra in the visible region. How would they differ, for example would one ...
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1answer
148 views

Is it possible to make broad spectrum light absorbing paint?

Is there such a paint / pigment that absorbs most wavelengths of light (beyond the visible light range) that can be used for solar heat generating applications? If not, would it be possible to make ...
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3answers
40 views

Luminescent materials under IR radiation?

is there a database somewhere of materials that are luminescent when exposed to Infra Red radiation?
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1answer
41 views

Hooke's Law for absorption spectra

Does anyone happen to know who was the first to use Hooke's law to model vibrational absorption peak frequencies/wavenumbers? I know Hooke's law is first outlined here: R. Hooke, Potentia ...
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1answer
82 views

Salt Analysis using spectroscopy

A few days ago, I learned the lengthy process of salt analysis during my practicals. The process is based on deductive reasoning but is too lengthy. What I am thinking is, can't it be done using the ...
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31 views

Finding the thermodynamics of protein unfolding from temperature and absorbance using fluorescence spectroscopy?

I recently did an experiment on protein unfolding using a Perkin Elmer fluorescence spectrometer. The protein was $\alpha$-chymotrypsin. I was given this paper for my procedure. I am now trying to ...
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41 views

Echelle Monochromators

"For any given order, the wavelength dispersion is approximately linear. but the dispersion is relatively small at lower orders or higher wavelengths." As you can see, wavelength dispersion and ...
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1answer
233 views

What is the effect of conjugation of a carbonyl group in IR spectroscopy?

Doing an exchange term so I've missed some classes that the others have attended, and unfortunately we're getting contradictionary explanations, so I thought I'd try and ask you. Would be extremely ...
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1answer
51 views

Where can I find the infrared band positions for phosphorus compounds?

I am trying to interpret an IR spectrum where I have $\ce{(NPCl2)3}$ I have $\ce{P-N}$, $\ce{P=N}$ and $\ce{P-Cl}$ bonds and it is cyclic. Where can I find or does anyone know what the general ...
2
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1answer
36 views

How is 2D spectroscopy able to show quantum coherent transport through networks?

For wave-like (quantum coherent) energy transfer in networks (eg. propagation of excitation in photosynthetic protein complexes of algae or FMO complex in plants) 2D electronic (photon echo?) ...
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1answer
98 views

Why is there a doublet instead of a singlet in this Wittig reaction salt configuration NMR?

I did an NMR sample to my salt p-carboxybenzyl triphenylphosphonium bromide. I got a doublet at 5.26, and according to every article it belongs to the $CH_2$ next to $P^+$, but how come I didn't get a ...
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1answer
55 views

Why are square planar coordination compounds with four different ligands optically inactive?

Why square planar co- ordination compounds of type Mabcd do not show optical activity, although they contain 4 different ligands ( i.e. chiral central metal atom)
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1answer
15 views

How can we measure electronic excitation in some “nm”(nanometres)?

I have no idea to which concept this belongs: The widest range over which electronic excitations in organic compounds occur, is A) 200 nm – 780 nm B) 220 nm– 500nm C) 250 nm– 700 ...
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1answer
73 views

Which vibrational modes of CO2 and CSO do not lead to IR absorption bands?

I recently came across this question, I have no idea about IR: Which of the following vibrational modes show no IR absorption bands? A) Symmetric CO2 stretch B) Antisymmetric CO2 ...
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22 views

Cation exchange capacity via IR spectroscopy? Is it as good as barium exchange? What is the intutition on how it works?

Cation exchange capacity is often regarded as the single best summary statistic for soil fertility. Years ago, I learned how to measure it myself, in a soil lab. I used compulsive barium exchange, ...
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20 views

Assign symmetric and antisymmetric stetches in IR spectroscopy

Typically the antisymmetric stretch in IR spectroscopy is higher than the symmetric stretch for a given functional group. For example for NO2 the antisymmetric stretch falls at ~1530 cm-1 compared to ...
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15 views

Raman Depolarization Ratio

What is the Raman depolarization ratio? What is a depolarized band, and what does it corresponds to in the structure of a molecule?
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32 views

General methods of Analysis for FTIR Results

What can we say about a molecule from the position and number of bands in FTIR spectrum. I know that the more symmetric a molecule is, the less number of bands it has. What else can we say, for ...
2
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1answer
37 views

Factors to consider to predict EPR

What are the factors to consider when predicting the EPR spectrum of $\ce{Cu(Ox)P(CH3)3}$ where $\ce{OX}$ is the oxalate ion? I understand that there are several factors to consider for EPR (Electron ...
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2answers
31 views

Optical Density numbers

If it's OD of 600nm I know that's the wavelength used, but what are the other numbers in something like "OD 600nm of 0.6-0.7". The 0.6-0.7?
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1answer
814 views

Is carbon dioxide IR inactive?

I am told that carbon dioxide is IR inactive. This somehow strikes me as untrue or at best oversimplified, because yes, it is overall symmetrical, but can't $\ce{CO2}$ be induced to show asymmetric ...
6
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1answer
269 views

Interpretation of TD-DFT results

For the first time I'm doing TD-DFT calculations (wB97XD functional) in Gaussian 09 for an open-shell system and the results look like the hell of a mess for me. The molecule is rather big, so I ...
5
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1answer
265 views

How can I deduce the linearity of XeF2 from the IR spectrum?

The vibrational modes of $\ce{XeF2}$ are at $555$, $515$, and $213~\mathrm{cm^{-1}}$ but only two are IR active. Explain why this is consistent with $\ce{XeF2}$ having a linear structure. From what ...
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1answer
118 views

HNMR Assignment

I have a molecule and i need to assign the hnmr. I have a printed spectrum So far my answer is: chemical shift_______splitting pattern_______coupling constant ...
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2answers
248 views

What splitting pattern is this?

I am trying to find the structure of an unknown molecule. What is the splitting pattern of these sets of lines? I think my unknown molecule is butanol and the hydrogens this splitting pattern is ...
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3answers
181 views

Nanoscopy Nobel Prize - why are all the tools in the visible light range?

It seems like all the new advances in molecular imaging/microscopy are in the visible light range of the EM spectrum. An example would be the most recent Nobel Prize for Chemistry. Is there some ...
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336 views

Proton NMR signals and rings

Does pyridine or furan have the more shielded proton NMR signals? I know that both are aromatic, so both have rather deshielded signals due to ring current combining constructively with the applied ...
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1answer
62 views

Chemdoodle to mestranova

Is it possible to copy my chemdoodle displayed structure into mestranovea? I have tried simple dragging (mac) and all the various copy/paste options... any ideas?