Questions tagged [spectroscopy]

Use this tag for questions about spectroscopic methods in practice and in theory, especially where more specific tags for the individual method (such as [nmr-spectroscopy] or [ir-spectroscopy]) are not available.

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30 views

Why photons with longer wave length demonstrate more active scatter and transmit that shorter length?

Why photons with longer wave length demonstrate more active scatter and transmit that shorter length? This troubles me to understand why NIR and Infra-Red goes through diffused media when compared to ...
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1answer
420 views

Where can I find (citable) FTIR spectra of CuCl and CuCl2?

I can't seem to find any published/citable infrared (FTIR) spectra in the 4000-400 cm-1 range of CuCl and CuCl2. Does anyone know of a source available, either free or paid?
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How to determine interaction of photon with a hydrocarbon Bixin

Bixin is an apocarotenoid found in annatto with 25 carbons with carboxylic acids at each end of the chain. It is an insoluble orange red pigment. I am interested to study photon interaction with ...
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1answer
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Derivation of the Orgel diagram for octahedral d2 complexes

The Orgel diagram for a typical octahedral $\mathrm{d^2}$ complex is shown below: (source: Kettle, Physical Inorganic Chemistry, p 146) I understand that the right-hand half of the graph shows how ...
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2answers
214 views

Functionalization of nanoparticles

I want to functionalize silver nanoparticles with thiol group. My question is "how can I find that the thiolated compound is attached to the surface of nanoparticles or not?"
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1answer
2k views

Why is the force constant for double and triple bonds approximately double and triple of that of a single bonds?

I am new to spectroscopy, and I am referring to Donald Pavia's Introduction to Spectroscopy. I came across this statement in the book, under the chapter Infrared Spectroscopy: $K$ is a constant ...
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3answers
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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 signal ...
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1answer
143 views

Why is more than one spectral line created on the de ecxitiation of a hydrogen atom [closed]

When an electron is de excited from a higher energy level to a lower one only one lone fits the bill then why is it that so many lines are created example n=4 to n=1
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1answer
497 views

Spectroscopy of excited state lithium

I have used data from a question regarding the reciprocal wavelengths observed when lithium transitions from excited states to a common ground state. The lowest energy transition is from n=3 to n=2. ...
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2answers
312 views

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?
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1answer
809 views

What are the microstates of the triplet oxygen molecule?

I am trying to understand molecular term symbols of oxygen molecule. Everywhere I looked, it is claimed that the molecule has 6 microstates, three of them are singlet, and three of them are triplet. ...
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3answers
548 views

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 ...
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How to solve the Schrödinger equation of 1D hindered rotor?

I have the following equation: $$-\frac{{{\hbar }^{2}}}{2I{}_{r}}\frac{{{d}^{2}}\psi }{d{{\theta }^{2}}}+V\left( \theta \right)\psi =E\psi, $$ with $$V\left( \theta \right)=a+\sum\limits_{n=1}^{...
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2answers
269 views

Potential wells and symmetry in absorption spectroscopy

In a course I am following, we are analyzing the potential wells in molecular absorption spectroscopy. For molecules with more than one normal mode, we can study the potential wells involved in ...
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71 views

Does the frequency of incident light change in Beer-Lambert Law?

The Beer-Lambert law is meant to describe the interaction between a solute and incident light. But, does the frequency of the light here change due to the interaction with molecules? I think there ...
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1answer
2k views

What is the proton NMR spectrum of p-methoxyphenol?

I think there will be two pairs of doublets, since the hydrogens adjacent to the $\ce{OCH3}$ and those adjacent to the $\ce{OH}$ group will be in different environments. The answer, however, is that ...
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151 views

Why is the number of carbonyl stretches in the IR spectrum different for solid state samples compared to samples in solution?

I am comparing two IR spectrums of the same molecule, one in the solid state and one in $\ce{CH2Cl2}$ solution. There is only one CO group in the molecule. Why does the solid state spectrum show two ...
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1answer
53 views

What are common procedures for lab absorption spectroscopy of gases?

I'm doing research for applications of absorption spectroscopy. I'm trying to find common practices such as how the gasses are mixed, measured, contained, and discarded. The gases involved will be ...
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1answer
245 views

Spectrochemical series of TMs: why does the field-splitting parameter NOT steadily increase along a period?

Why doesn't the field splitting parameter increase steadily along the period for 3rd-row transition metals, as one would expect due to a better energy match between ligands and the metal as $Z_\mathrm{...
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1answer
58 views

Is NMR possible using nitrogen as the nucleus? [closed]

Is NMR spectroscopy performed using nitrogen nuclei? If yes, then where?
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1answer
205 views

Spectroscopy pyrazine molecule

Considering pyridazine and pyrazine molecules, I am asked to say if I can distinguish one from the other in a sample. I supposed that is possible because pyrazine belongs to D2h and so it has the ...
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1answer
270 views

Wavenumber range reversed in IR spectroscopy

I recently stumbled upon a result table from an IR spectroscopy, that is an image full of peaks. The goal was to decide which peak belongs to which group by looking up the intervals in a related table....
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1answer
17k views

Ring Strain and C=O Stretching Frequency

Why does $\ce{C=O}$ stretching frequency increase with ring strain? Why does conjugation decrease $\ce{C=O}$ ring strain? I am told that cyclopropanone exhibits a higher $\ce{C=O}$ stretching ...
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2answers
168 views

Gas spectra in the 400 nm - 1000 nm range

Disclaimer: My background is computer science. Is it possible to detect any gas using a visible light and near infrared (400 nm - 1000 nm) hyper spectral imaging camera? This can be related to gas ...
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1answer
470 views

Expected accuracy of experimental IR spectra compared to literature reference

I have a table from a journal which indicated signals of an alpha chitin that I used as theoretical values. I did my own analysis to identify a chitin sample and it had signals that slightly varied ...
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1answer
325 views

Spectroscopic transition frequency

I have difficulty understanding the first sentence of the Introduction in the paper linked below. Can someone explain to me what is spectroscopic transition frequency and thermal bath? The ...
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Does the laser side of laser fluorescence spectroscopy have to be so complicated?

I understand the working principle behind zapping some gas and looking at spectral emissions, and I can see why photodetection is so difficult. But I thought that pointing a laser into a vacuum ...
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2answers
927 views

Bond of interest

What does it mean for our bond of interest if we have low bond length and high frequency? Trying to make this connection but am not understanding. If anyone could explain it intuitively, that would be ...
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926 views

Period of Vibrational Modes

I am trying to understand more about the period of vibrational nodes. Currently, I am interested in the wavelength of the $\ce{Si-O}$ bond stretch in silica. I think this value is roughly $1000\mathrm{...
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The best method(s) to identify/verify the presence of a small organic molecule [closed]

What is the fastest or the most definite method (preferentially a single unexpensive method) for verifying the presence of a certain small orgnic molecule which is expected to be of >90% purity in a "...
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1answer
880 views

“NBO diagrams” versus MO diagrams

Molecular orbital diagrams are well known by chemists. According to Wikipedia (emphasis mine), A molecular orbital diagram, or MO diagram, is a qualitative descriptive tool explaining chemical ...
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2answers
211 views

When does ratiometric measurement account for signal variations?

I've been reading about pH and ion sensors that rely on a ratiometric approach, which supposedly circumvents many problems of intensity-based methods such as dye bleaching, dye leaching, and ...
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2answers
129 views

How to measure absorbance at 882 nm?

I am trying to measure the absorbance of a solution at 882 nm, but this seems to be beyond the range of many UV-Vis spectrometers. Is this a job for the IR spectroscopy, or something else? I do not ...
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3answers
779 views

What are the requirements for FRET?

I have a question about fluorescence resonance energy transfer (FRET), and the requirements needed for this technique. Q: Which of the following need to be met for FRET? A) Strong overlap between ...
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4answers
6k views

Why don't equivalent hydrogens cause splitting in NMR?

When doing NMR spectroscopy, it is an observed fact that equivalent hydrogens do not split one another. Why don't equivalent hydrogens split each other's signals? For example, why is the NMR spectrum ...
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1answer
433 views

Determining Structure of molecule based on IR Spectra and HNMR data [closed]

I have been given the following data and am asked to determine what the structure is. So far based on the IR spectra given I (think) I have identified a $\ce{C-O}$ bond, $\ce{sp^3}$ $\ce{C-H}$ bond ...
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1answer
221 views

Does the triplet sigma state of a diatomic molecule experience 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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1answer
963 views

Explanation for increasing wave number trends for hydrocarbons

At my university, we had an organic chemistry exam question that stated,"The trend in the values of the ir absorbtions for the c-h bonds of methane ($\ce{CH4}$: $2995\,\mathrm{cm}^{-1}$), (ethylene: $...
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1answer
1k views

Effect of nuclear spin statistics on the IR spectrum of CO2

Specifically, I am talking about $\ce{C^{16}O2}$. With a nuclear spin of zero meaning, it is a boson - it's total wavefunction must be totally symmetric. The total wavefunction is made up of an ...
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3answers
3k views

Determining structure using HNMR and IR

I have a homework problem where I'm to draw the structure of a compound of molecular formula $\ce{C10H12O2}$ using the following IR data and $^1$H NMR spectrum: IR absorption at 1718 cm$^{-1}$ NMR ...
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1answer
18k views

Calculating purity from NMR spectrum

I just started organic chemistry in university. I have no idea what I'm doing — it's wonderful. My assignment was to produce $\pu{10g}$ of fluorescein, the theoretical yield is $70~\%$ — I need at ...
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1answer
999 views

Why convert benzoate in soda to benzoic acid for spectroscopy experiment?

I did an experiment where I analyzed the amount of caffeine and benzoate in soda via spectroscopy. I've got the absorbances and did all the math for everything, but I'm having a hard time figuring out ...
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4answers
116k views

Why are there multiple lines in the hydrogen line spectrum?

Hydrogen has only one electron, yet it exhibits multiple lines in a spectral series, why is this?
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3answers
204 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 ...
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3answers
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Could someone please explain the difference between m/z and m/e in mass spectroscopy

The definition: The abbreviation m/z is used to denote the dimensionless quantity formed by dividing the mass number of an ion by its charge number. It has long been called the mass-to-charge ratio ...
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1answer
755 views

OH band in IR of propyl ethanoate? [closed]

In lab I combined 1-propanol with acetic acid to make propyl ethanoate. I obtained an HNMR and an IR of the product. The HNMR suggests that the product was successfully synthesized. The IR has the ...
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0answers
295 views

Spectral analysis of periodic table of elements in time domain

I'm trying to get the spectral analysis data of the periodic table of elements in the time domain format or find a site that has the data in the time domain format. All the sites I know have the data ...
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1answer
2k views

Rotational Constant for CO2 from an IR Vibrational-Rotational spectra

I have been trying to calculate the rotational constants ($B$) for $\ce{CO}$ and $\ce{CO2}$ from IR Vibrational-Rotational spectra. I know that for $\ce{CO}$ the peak spacing is approximately $2B$ (...
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1answer
734 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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2answers
97 views

how to determine timescale with characterization methods?

There are 4 different timescales on material characterization (as classified in the Atkins textbook ): a)Time during which a quantum of radiation or a particle can interact with a molecule. b)...

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