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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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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23 views

Possible ionization and fragmentation of chemicals [on hold]

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
20 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?
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26 views

Choosing the instrumental techniques for chemical analysis [on hold]

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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14 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 ...
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33 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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12 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
34 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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30 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 ...
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17 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 ...
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23 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 ...
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60 views

How to interpret orbital transition in TDDFT?

Consider the following TDDFT run with GAMESS: ...
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2answers
172 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
27 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, ...
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20 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
30 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, ...
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18 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 ...
3
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1answer
25 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: ...
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1answer
85 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, ...
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1answer
34 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 ...
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1answer
106 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 ...
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1answer
46 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
48 views

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 ...
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1answer
57 views

What are the spectroscopic signatures that differentiate triple state water from water at 1 atm?

According to the Wikipedia article Triple point of water, the triple point of water occurs at The single combination of pressure and temperature at which liquid water, solid ice, and water vapor ...
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1answer
33 views

Infrared spectroscopy of substances on a OHP film

How can we record a IR spectrum of a substance coated on a Over Head Projector (OHP) sheet? instrument has both transmission and ATR modes. IR spectrum is to be recorded for both the OHP sheet as well ...
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35 views

Why do electronegative heteroatoms increase C=O stretching frequency (bond strength)

Why does a more electronegative heteroatom (i.e. $\ce{Cl}$ or $\ce{O}$) increase the stretching frequency of a carbonyl? I'd suspect it's that they donate their lone pairs and we end up with a ...
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1answer
44 views

Spectral Peak-Picking in MS Excel

I'm working often with spectral data of various gases, and the bulk of the data analysis is assigning the peaks with maximum signal (y-axis) to frequency (x-axis). Often we have several thousand data ...
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1answer
13 views

What is this reference material in spectrophotometry?

First, I should say I never have done any spectroscopies and I am just reading about it. As far as I know, UV-Vis spectrophotometer has 2 beam samples: sample and reference. The sample has very ...
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1answer
65 views

What happens to chemical shifts of protons close to aromatic systems in ¹H-NMR?

I have two questions regarding chemical shifts on aromatic systems. First, what does being near an aromatic system do to protons? If we look at the spectra of 1-napthalenemethanol and then ...
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33 views

Spectral reflectance identification of types of iron rust

According to the Wikipedia page about rust, there are red and green types of rust that occur on iron. Red rust is the reaction with oxygen and water and the green with chlorine (in oxygen poor ...
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2answers
93 views

How to calculate vibrational spectra of organic molecules?

I watched a ted talk (Luca Turin: The science of scent) and was wondering if anyone had any examples of how to calculate vibrational spectra of molecules (used as fragrances)? Would love to figure ...
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63 views

How to find pKa given absorbances and pH [closed]

If the absorbance of one of the buffer solutions (pH = 4.623) was 0.319 and the absorbance of the basic solution was 0.625, what is the $\mathrm{p}K_\mathrm{a}$ of the indicator? Include activity ...
3
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1answer
33 views

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 ...
5
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1answer
62 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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83 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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50 views

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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56 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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1answer
40 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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41 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
454 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 ...
3
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1answer
49 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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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. ...
5
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54 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 ...
3
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1answer
72 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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2answers
117 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?
5
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1answer
64 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
119 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 ...
4
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1answer
40 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 ...
4
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1answer
64 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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96 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 ...