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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Raman signal of black matte object

I was trying to identify the material of this sediment filter cap whether it is really Polypropylene but i couldnt get a good signal but only noises no matter the exposure and time (my raman ...
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Formulas for the number of spectral lines

While reading through Narendra Avasthi's Problems in Physical Chemistry, I came across two formulas on p. 64 (Scanned page): When electrons de-excite from higher energy level ($n_2$) to lower ...
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Alternating heavy metal materials analysis

If someone had a material that was made of alternating heavy metals (ABAB) and each layer was 1 micrometer thick, would an electron beam be able to displace electrons in the lower layers? If these ...
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How does using a triode setup of an electron gun create a stable electron emission? [closed]

If a triode is an electronic amplifying vacuum tube how can this be combined with a electron gun to create a gun that produces a more stable electron emission? What is the set up when this is done? Is ...
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Analyzing alternating metals in a polymer matrix with 1 micrometer depth and only 10% metal

This is a theoretical question that I am struggling to get started on for a seminar discussion. If you were attempting to design an instrument with all the basic components (source, analyzer, detector,...
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Does increasing the number of interferometers increase signal in FT-IR?

I'm trying to understand why most modern FT-IRs have three interferometers. Does this improve the signal in someway or does it have another effect?
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Is the Hydrogen spectrum only an emission spectrum?

In a statement question it was stated that hydrogen spectrum is an emission spectrum and the scheme considered it to be ture. But my argument is that it can be both emission and abosorption spectrum. ...
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Resources on the mechanism of Everhart-Thornley electron detector?

I'm trying to find some fundamental resources that explain the basic principals, components and applications of an Evenhart-Thornley Electron detector. It seems like there is limited "basic" ...
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How would you examine samples of rocks using a handheld spectrometer?

My friend has an old spectrometer set that his father used to own and we are trying to figure out how to use it. Asking his father about it is not an option unfortunately. The box contains a handheld ...
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Implications of the excitation spectra

The fluorescence excitation spectra show the change in fluorescence intensity as a function of the wavelength of the excitation light. I'm interested in the certain physical implications of the above. ...
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Point group specific definition

Does the term only refer to molecules that have the same symmetry elements or exactly the same symmetry operations. Online I see that its the same symmetry operation however my professor's slides show ...
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For Fe2O3 what could an XPS peak at 711.9 eV mean

For an XPS spectra of Fe2O3 film on graphite there are peaks at Fe 2p1/2 = 724.2 eV and Fe2p3/2 = 709 eV but there is another peak at 711.9 eV that I can't identify. Any ideas on what this might be ...
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CDCl3 peak in NMR spectra

I need to determine where is my $\ce{CDCl3}$ peak in my NMR spectra of 3-methylbenzoic acid. The thing is that I read somewhere that the peak should be at $\pu{7.24 ppm}$ but there is a lot of peak in ...
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What are the advantages of using ellipsometry over AFM to determine film thickness?

I am trying to understand why one would chose one over the other and I am struggling to understand this since both are non destructive. I know AFM can only go at 5 nm but other than that I don't see ...
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Why would Auger electron detection have potential for higher spatial resolution than EDX

I understand that Auger electrons are emitted when an electron falls from a higher energy level to a open inner shell and EDX uses electrons that fall from outer shells when an inner shell is kicked ...
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1answer
129 views

Plotting the data using Beer-Lambert law [closed]

For the spectroscopy lab we had a stock dye ($\pu{1.00E-4 M}$ Erioglaucine Blue) that we had to dilute. We had to dilute $\pu{1 mL},$ $\pu{3 mL},$ $\pu{5 mL},$ $\pu{8 mL},$ and $\pu{10 mL}$ in $\pu{...
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CNT Raman ratio of G band to 2D band?

I believe that the G band (~1600 cm-1) shows the stretching mode of the graphene in a carbon nanotube (e.g. chiral, zigzag, armchair) and the 2D band (~2680 cm-1) shows the number of walls in the CNT. ...
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1answer
109 views

DCC coupling of N-hydroxysuccinimide and 2,2-dimethoxyacetic acid

I am forming N-hydroxysuccinimide ester (1) by DCC coupling with N-hydroxysuccinimide and 2,2-dimethoxyacetic acid using distilled THF as solvent. What I see on $\ce{^1H}$-NMR is three major singlets:...
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In SAXS experiment, you observe strong Bragg peaks at q values of x, y and z. What are the d-spacings of the corresponding diffracting planes?

If d=2pi/q then would it simply be that d=2pi/x, 2pi/y and 2pi/z? This feels to simple and i feel like maybe some version of the 4pisin(theta)/lambda equation should be here soemwhere but I cant ...
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Mechanism of decomposition of alkali metal halides in flames

A student recently asked an interesting question What happens when KCl is introduced in the Bunsen flame?. This apparently simply question led me to an interesting debate. We all know that emission of ...
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2answers
481 views

What is happening when KCl burns in a bunsen flame? [closed]

I did the experiment to qualitatively observe the different colours given off by different salts when placed in a flame. But what is actually happening to the salt ? Take $\ce {KCl}$ for example. Does ...
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How is a photoelectron spectrum assigned?

The photoelectron spectrum of a given molecule is commonly used as experimental evidence of the energy ordering of molecular orbitals (See here: 10.4: Photoelectron Spectroscopy, and many other ...
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Is acetylene IR active? [closed]

I've a very straight forward question, I'm confused because I've been told that a atom which has a oscillating transient/permanent dipole is IR active. But there are few asymmetric stretching/bending ...
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Estimate the relative intensities of absorption given the split in energy levels

Estimate the relative intensities at $\pu{25 °C}$ of absorption originated in the ground state and the first excited state when the energy levels involved are separated by: (a) $\pu{10000 cm^-1};$ (b) ...
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Statistical methods used for testing the homogeneity of the sample

So, if I have multiple FTIR spectra each taken on different location of the sample and averaged from ~20 spectra, how can I check if the sample is homogeneous, i.e., if there are statistically ...
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1answer
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Could coating silver inside of a cuvette be used for SERS?

I understand that molecules adsorbed to a coinage metal surface experience plasmonic enhanced Raman shifts and I have a spectrometer that I would like to perform SERS measurements with but do not have ...
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Looking for a dye which emits around 680 nm

For a specific experiment, I'm looking for a dye which would emit around 680 nm. Preferably one I could buy easily commercially. Are there any databases which might give the emission spectra of ...
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1answer
98 views

Can you measure an IR spectrum of a sample inside a glass vial?

If I have a sample of some compounds dissolved in water inside a glass vial (let's say quartz). Would it be possible to get a usable measurement through this glass vial without too much absorption by ...
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1answer
52 views

Overview of material characterization methods

I have been searching for quite some time now, but I feel like it is impossible to find some sort of chart where I can determine which characterization method (microscopy, spectroscopy, ...
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How is Pi antibonding orbital more polar than Pi bonding orbital?

While reading about the solvent effect on electronic transition in ESR spectroscopy, I found it written somewhere that the pi anti-bonding orbitals are more polar compared to pi bonding orbitals. Can ...
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1answer
67 views

Open source for atomic spectra raw data

Is anyone aware of a open source atomic spectra database? In particular I am looking for high resolution Na atomic emission which can be downloaded in csv or Excel. I am aware of NIST but I could not ...
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Photoluminescence Spectra of Solids

What information can we gain with the photoluminescence spectra of solids? The bandgap can be determined for example, but are there any other useful properties we can learn? I care about this in the ...
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1answer
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Determining electronic configuration [closed]

One writes the electronic configuration in terms of shells, spdf subshells, orbitals, and spin of electrons. There are exceptions to principles we know. How does one confirm that the way of writing is ...
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1answer
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Detectable elements using flame AES

I've been looking for extra information concerning flame atomic emission spectroscopy. I need a clear overview of which elements are detectable with this technique, but I can't find anything because ...
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1answer
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Difference in peaks in EDS and XPS spectra

I have been reading some papers on XPS and EDS and I saw that there's a difference between the width of the peaks (of the same material) in XPS and EDS. Is the reason for this difference because of ...
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Haemoglobin literature spectra does not match

I am studying haemoglobin absorption spectra in its oxygenated and deoxygenated state and I compiled values from different sources including: A PhD thesis by van Assendelft [1], using extinction ...
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1answer
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XPS/EDS vs FTIR/Raman [closed]

So I have been studying the four methods the past couple of weeks. To my understanding, XPS is a very surface-sensitive technique. It can give information about the composition of the surface but also ...
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Raman or FTIR spectroscopy to identify metals?

Metals are opaque, so doesn't most of the light reflect? And does the IR source even cause vibrations in the metal? Same goes for Raman spectroscopy, is it useful for use of metal identification? Is ...
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3answers
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How to simulate a Lorentzian broadened spectrum in MATLAB?

I'm trying to simulate the 2nu2 band of HCN in MATLAB. I generate a stick spectrum from the data I have (taken from the HITRAN database) and then use conv() to ...
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Solving the Schrödinger equation for a rotating triatomic linear molecule

This source is showing that solving the Schrödinger equation for a triatmoic linear molecule yields the same formula for the rotationaI quantum states $BJ(J+1)$ as for dipoles. For dipoles, the total ...
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1answer
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Reason for same frequency of spectral line in infrared and visible region

I encountered this question while trying to understand the basics of spectroscopy and atomic structure. Which electronic transition in Balmer series of hydrogen atom has same frequency as that of n=6 ...
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What does Brightness/ intensity of spectral lines depend on?

My book states that it depends upon "The number of photons of same frequency or wavelength ABSORBED or EMITTED" From what I understood, if many hydrogen atoms within the discharge tube EMIT the same ...
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3answers
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Carbon in Glass - XPS Analysis

I was reading a paper and found this elemental XPS analysis of an unmodified microscope glass slide surface. C (1s): 17.7% Si (2p): 28.47% O (1s): 53.83% It seems strange for a piece of normal ...
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Is it true that heavy water is not blue?

I believe I saw this claim somewhere on the internet a long time ago. Specifically, it was claimed that the difference could be observed by filling one long, straight tube with light water and one ...
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What is the difference between quantities reported as optical rotation and circular birefringence?

Optical activity gets complicated quickly and the following question is intended to avoid threshold confusion. The linked lecture note* seems very accessible to me and Table 10.6 in particular is ...
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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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Differences in Novichok agent mass spectra

As we have all heard, in 2018, a series of poisonings with a nerve agent alleged to be of the Novichok series was carried out on British soil. It is claimed that the agent used was A-234. However, a ...
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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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Deriving the absorption coefficient from state transitions

This source states that the absorption coefficient $\gamma$ is proportional to the difference in particle number density $\Delta n$ per unit volume between the initial and the final rotational state ...
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1answer
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On the detection of molecules in electrospray ionisation (ESI)

Of the ESI spectra that I have encountered, positive & negative mode, the detected species always have charge (positive or negative) corresponding to the charge mode that the machine is in. Is it ...

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