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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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Do these Raman scan output files really belong to the same exact Raman scan?

What I have got: Two files from First Defender’s system named Scan227-dark.spc and Scan227.spc. Plain text versions of both files: plaintextOfScan227-darkspc.txt and plaintextOfScan227spc.txt. Image ...
AbelBp's user avatar
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3 votes
2 answers
99 views

Why aren't there different peaks for different IE in PhotoElectron Spectroscopy (PES)?

The way I understand PES is that you shine a light on a bunch of atoms and measure the kinetic energy of photons to determine ionisation energies (or energies of electrons... is that different?). I ...
Maddy's user avatar
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2 votes
2 answers
67 views

Atomization and excitation in AES

AES (atomic emission spectroscopy) is often mentioned as both quantitative and qualitative analyzing method. From this site Atomic Emission Spectroscopy the sources such as flame and ICP are used. ...
Shira's user avatar
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2 votes
1 answer
77 views

Flame atomic absorption spectrophotometry: can it detect anions?

My teacher said that AAS doesn't work for non-metals - only works for cations. I asked why and he said that was how things go. Now, perhaps someone could give a more fulfilling explanation? Is that ...
Percival the caterpillar's user avatar
3 votes
1 answer
420 views

How to find the infrared absorption spectrum of O2 and N2?

I am new to spectroscopy, so I am not sure how my questions are perceived. I just want to make sure that I am not lost, so any kind of suggestion is welcome. I am interested in the infrared absorption ...
kolmogorov's user avatar
5 votes
1 answer
240 views

Rotational spectroscopy of diatomic molecules

It is said rotational spectra of homonuclear diatomic molecules cannot be observed but why? In the book (Banwell, C. N. 1994. Fundamentals of Molecular Spectroscopy.) It says, for homonuclear diatomic ...
Physics's user avatar
  • 61
8 votes
2 answers
646 views

FTIR Spectra: Did I synthesize ethyl gallate from gallic acid?

I successfully synthesized ethyl gallate from gallic acid and ethanol (of course there are other reagents too, like DCC and Pyridine). Before conducting FTIR analysis, I performed column ...
Jonathan's user avatar
  • 155
2 votes
0 answers
37 views

Do σ→π* and/or π→σ* transitions occur in ultraviolet spectroscopy?

I was taught that the only transition that occur in UV-vis spectroscopy are: σ→σ* π→π* n→π* n→σ* Wikipedia seems to support this claim but I have trouble understanding why this must be the case. ...
Frisk17's user avatar
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11 votes
0 answers
74 views

Doubt in Zeeman effect for sodium spectrum

I am reading an atomic molecular physics book (for Indian universities). You may not familiar with it. But you can download it from the link if you wish. So in the book it is mentioned that for normal ...
Sagar K. Biswal's user avatar
0 votes
0 answers
26 views

FTIR data: Is there a way to obtain stat significant differences observed between groups in LD-PCA?

Besides checking the loadings and choosing peaks of interest, there is a way to point out from the LD-PCA or PCA the differences between groups that are significant? All ideas are very much ...
Microbiologie13's user avatar
3 votes
0 answers
44 views

Calculate percent composition from XPS?

I have an XPS graph and was wondering how to calculate percent composition. I do have the percent compositions that were determined from the graph, but I don't know how they were found. For reference, ...
lzzard's user avatar
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1 vote
2 answers
53 views

Photochemistry/Physicalchemistry - Fluorescence & Solvent Form

The hint from my instructor for the answer is related to Jablonski Diagram. The scenario: using fluorometer to measure fluorescence of a compound. How would my fluorescence results differ when ...
Syrianmousediggingsand's user avatar
1 vote
1 answer
87 views

Is the energy difference between the 2s and 2p orbital smaller than the difference between 3s and 3p?

on this website (https://physics.nist.gov/PhysRefData/ASD/levels_form.html), you can look up atomic spectra. For example, if you query "Na I", you will see that the Level (cm^-1) for the ...
Theiserino's user avatar
1 vote
0 answers
17 views

Is there any uv-vis sensor that installs on a pipe like other measurement tools like flowmeter or temperature sensor?

I am looking for an industrial UV-vis sensor that is installed on a pipe like other measurement instruments like temperature and flow transmitters. I researched this subject and I found one model but ...
jasw's user avatar
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0 answers
91 views

Multiplicity and signals of cis−[(Ph3P)2PtF2] in two NMR spectra

I am interested in the number of the signals and their multiplicities in the $\ce{^{31}P\{^1H\}}$ and $\ce{^{19}F\{^1H}\}$ NMR spectra of $\ce{[\textit{cis-}(Ph3P)2PtF2]}$. It is given that $\ce{Pt}$ ...
MathEnthusiast's user avatar
5 votes
1 answer
898 views

Help interpreting IR Spectrum of Vanillin ("aldehyde bands")

I'm not sure about the attributions of 3 bands of my ATR FT-IR spectrum of an extract of vanilla sugar, that probably contains mainly vanillin and some impurities. The extraction solvent was ethyl ...
dispatchh's user avatar
3 votes
0 answers
28 views

Can multispectral imaging be used for identification of materials, substituting for hyperspectral imaging?

Nowadays a lot of research and applications are using Hyperspectral Imaging for identification and segregation of plastics by material. But the cost of a HSI system is quite high. Could a ...
Aether's user avatar
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2 votes
0 answers
47 views

Negative absorption coefficient

What does a negative absorption coefficient mean? In detail - I participated in a Synchrotron virtual laboratory. I have to analyze the results and understand what a negative absorption coefficient ...
Roni Amit's user avatar
0 votes
0 answers
52 views

XRD experiment: how to interpret data and solve crystal structure from 2theta vs intensity values

I have just performed an XRD (X ray diffraction) experiment (powder), but the XRD machine I have used is not able to describe crystal data, I have $2\theta$ and intensity in arbitrary units in a UXD ...
Ștefan Dumitrescu's user avatar
0 votes
1 answer
102 views

Why does Raman Activity Require Anisotropic Polarizability?

Normal mode of a molecule needs to involve the change in molecular polarizability (anisotropic polarizability) to be Raman active. Explanation is provided in Physical Chemistry textbook by Atkins on ...
Dario Mirić's user avatar
0 votes
0 answers
79 views

Apparent color of nickel(II)chloride and nickel(II)chloride hexahydrate

Why does anhydrous nickel chloride (NiCl2) appear yellow, even though chloride ions are considered weak field ligands, which should result in a smaller ligand field splitting energy and the absorption ...
Mäßige's user avatar
  • 127
1 vote
1 answer
225 views

What shifts protons on a benzene ring to lower ppm?

Why do these protons appear at 6.9 and 6.93 ppm, at lower ppm value? I assumed it was due to the anisotropic effect, specifically I thought the circulating (pi) electrons induced a magnetic field ...
ilovecats's user avatar
0 votes
0 answers
29 views

What's the reason of curvature in Tanabe-Sugano diagrams?

Analysing Tanabe-Sugano diagrams it's evident that some of the lines are pretty parallels to that of the ground field whilst others are inclinated or have some curvature. I know what's the effect on ...
Chemistry.'s user avatar
-1 votes
1 answer
139 views

Convergence limit of emission spectra for atoms with multiple electrons

In high school chemistry, students are taught that the convergence limit in the emission spectrum of an element can be used to determine the first ionization energy. However, what about the second, ...
Rafael's user avatar
  • 249
2 votes
0 answers
41 views

Commutating operators of angular momenta

I've studied the formal procedure to pass from the uncoupled basis set of individual angular momenta to the coupled basis set of total angular momenta for polyelectronic atoms. I start from an ...
Chemistry.'s user avatar
1 vote
2 answers
100 views

Why don't I get a whole number when determining the vibrational energy level of F2? [closed]

This is a cross post from physics stackexchange. I hope to get more answers here, because I think chemists have more to do with such things. So I was playing around with some data and formulas and ...
iwab's user avatar
  • 359
-2 votes
1 answer
95 views

Doubt on vibronic transitions

When we justify the presence of electronic transitions forbidden by Laporte selection rule, the coupling between electronic and vibrational states help us. Why we say that in this way we are ...
Chemistry.'s user avatar
1 vote
0 answers
52 views

Are these formulas for the critical value for detection interchangeable?

I am trying to compare equations for calculating the critical value for detection. One is presented by the ISO standards (https://www.sciencedirect.com/science/article/pii/S0969804316306455?via%3Dihub)...
Elis Lovelace's user avatar
-2 votes
1 answer
39 views

What the book means for "percentage difference"?

From Atkins-De Paula, Physical Chemistry, Ninth Edition, page 485 Not sure what the books means as "percentage difference". Btw, this is my attempt Fundamental vibration, in wavenumber, ...
user3713179's user avatar
2 votes
0 answers
115 views

Calculating Rotational Temperature from an FTIR Spectrum

I am trying to calculate the rotational temperature of a sample of gas phase HCN from an FTIR spectrum. It's a 10 Torr sample in a 10 cm gas cell, held at room temperature. In theory, I should be able ...
Tkh97's user avatar
  • 367
9 votes
2 answers
383 views

Software to draw one-dimensional PES including vibrational energy levels

I am trying to represent the difference between the an anharmonic and harmonic treatment of vibrations. The easiest way to do this is to present an example of a harmonic and anharmonic potential ...
isolated matrix's user avatar
2 votes
2 answers
185 views

Datasets of Light Absorbance Spectra for Atmospheric Gases

I am currently doing some thermal/aerospace engineering research that involves finding light absorption in different points in Earth's orbit. What is the best way to find absorbance vs. wavelength ...
Ankit's user avatar
  • 129
2 votes
1 answer
138 views

Equipment recommendation for atomic absorption spectroscopy (AAS) testing for mercury, lead, and cadmium

I work in a public health laboratory in a small mining town and we have the chance to buy equipment to test for lead and cadmium in wastewater, and mercury in not just wastewater, but also in blood, ...
JPertuz's user avatar
  • 29
1 vote
0 answers
104 views

Franck-Condon principle and shift of wavelength

I was revisiting my notes for spectroscopy, and I came across the Franck-Condon-principle. I understand it well, but want to clear some doubts regarding this. I know that the Franck-Condon-principle ...
Mäßige's user avatar
  • 127
1 vote
0 answers
28 views

When a 7-membered ring is formed during GC/MS, does the substituent need to start with a carbon?

When looking at the GC/MS for Allylthiobenzene aka allyl phenyl sulphide, two clear peaks are seen at 91 m/z and 65 m/z, most common for 7 membered and 5 membered carbon rings respectively. The ...
anonymous plz's user avatar
2 votes
0 answers
62 views

Auxochrome groups and red shift

Wikipedia states that "An auxochrome is known as a compound that produces a batochromic shift, also known as a red shift because it increases the absorption wavelength, thus approaching infrared ...
Luckenberg's user avatar
4 votes
1 answer
83 views

Polyatomic molecule vibrational spectra - Molecular dipole expansion in Taylor series

To give some context: I am studying the molecular spectra in the context of an introductory course to atomic and molecular physics. My professor is using the transition rate expression from an initial ...
akkar's user avatar
  • 41
5 votes
1 answer
923 views

How to proceed with iodometric titration to determine caffeine concentration in liquid coffee?

Context I'm a high school student who decided to investigate the relationship between caffeine concentration and brewing temperature of coffee out of their love for the substance. For my method, I ...
qanpi's user avatar
  • 59
4 votes
1 answer
132 views

Does Warburg impedance predict zero DC current in an Electrode/Electroyte interface?

I'm trying to understand how/if the Warburg impedance, $Z_w$, of an electrode-electrolyte interface dominates the impedance at low frequencies. I cannot understand how this model can predict a DC ...
bes's user avatar
  • 41
5 votes
2 answers
100 views

How to get continuous spectral data into intensities of channels centered around wavelengths?

Currently, I am looking into using a spectral sensor from SparkFun in order to obtain spectroscopic data to feed into a trained neural network, however this sensor gives intensities based on inputs ...
soravoid's user avatar
-2 votes
1 answer
350 views

How to read 1H-NMR- and IR-spectre (for ibuprofen) [closed]

I have read the answers to related/similar questions. They didn't help. I have to read a proton-NMR-spectrum and an IR-spectrum of ibuprofen. The structure formula is given to: I have not been ...
Daniel's user avatar
  • 11
2 votes
0 answers
117 views

Explaining the low-lying electronic state of NO

The question asks the following: 'The molecule NO has a low-lying electronic state 0.015 eV above the ground electronic state. Explain why this is the case and state the electronic degeneracies of ...
Bartholomew696969's user avatar
2 votes
0 answers
120 views

Deduce the shapes of stretching modes of a tetrahedral molecule

This question is in relation to the [FeCl4]- molecule, which is tetrahedral. I previously deduced, using symmetry analysis, that the vectors corresponding to the bonds of the molecule will be A1+T2, ...
Bartholomew696969's user avatar
3 votes
1 answer
247 views

Why does H2O appear as spikes in IR of air?

In the IR of air shown below, the region for water at 1500 cm-1 is hard to individually assign peaks due to their "spikey" nature. Is there any specific reason for this or does it just ...
Audrix's user avatar
  • 137
2 votes
0 answers
88 views

The extinction coefficients of oxymyoglobin and ferryl myoglobin

I want to know what the extinction coefficients of oxymyoglobin and ferryl myoglobin are. I was able to find the one for the oxymyoglobin in this pretty old article (it says that it equals $121 \text{...
ChemistryGeek's user avatar
2 votes
0 answers
211 views

What is the origin of the spin selection rule?

Why is the change in total spin ∆S = 0 during an absorption of a photon, in contrast to the ∆L = ±1, where the photon transfers its angular momentum? I am aware that spin-orbit coupling breaks this, I ...
Furrier Transform's user avatar
3 votes
0 answers
38 views

Why does hydrogen bonding cause a broad stretch in IR spectroscopy?

So hydrogen bonding is an intermolecular forces. I'm assuming that the hydrogen bonding strength varies between molecules and some molecules won't undergo hydrogen bonding causing different bond ...
Blob's user avatar
  • 31
2 votes
2 answers
1k views

NH protons not appearing in H NMR spectrum of 3,4-dihydropyrimidone derivative (solvent: CDCl3)

My synthesized compound is 3,4-dihydropyrimidone derivative, which has 2 nitrogen in the ring. The $\ce{NH}$ protons are not appearing in the H NMR spectrum and the solvent used was deuterated ...
joe 's user avatar
  • 31
3 votes
1 answer
113 views

Why is the local coupling constant (vibronic coupling) given in eV?

Should the local coupling constant g not be without a unit, as the Holstein Hamiltonian suggests? $ H=\underbrace{\sum_{P, Q} h_{P Q}^{(0)} a_P^{\dagger} a_Q}_{\text{Fixed geometry}}+\underbrace{\sum_{...
P M's user avatar
  • 81
1 vote
0 answers
32 views

Why must the beta term in the rigid-rotator PDE take the form J(J+1)? [duplicate]

Here is the partial differential equation for which the solutions Y are are the wave functions for the rigid-rotator (Equation 5.5 in McQuarrie and Simon's Physical Chemistry). $$\sin\theta\frac{\...
Eli Jones's user avatar
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