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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7 views

Does using same calibration curve for chemical analysis introduce correlation in sample error/uncertainty values?

I am using a hypothetical case to explain my question Let us consider a chemical analysis method A (using a certain instrument), which is used to quantify the value of a particular species b. ...
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16 views

Negative DBE/Degree of Hydrogen Deficiency?

I tried calculating the Index of Hydrogen Deficiency for C6H15SiCl, and I get negative one. I get this value by subtracting the number of chlorine and hydrogen atoms from that of the carbon atoms, and ...
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23 views

How will we determine what to take as a reference in uv-vis spectrophotometer if a mixture is reacting? [closed]

If A+B+C+D is a reaction mixture in aqueous media in which A reacts with B and C reacts with D, what will be the best choice as a reference for colorimeter? How will you verify Lambert Beer's Law for ...
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How to interpret Energy-dispersive X-ray spectroscopy result? [closed]

Element Weight % Atomic % Error % C K 38.05 50.09 9.34 O K 40.44 39.96 10 NaK 3.24 2.23 10.73 MgK 0.77 0.5 15.05 ...
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20 views

Why hydrogen gas tube produce hydrogen atomic spectrum

To measure the atomic hydrogen spectrum people often uses hydrogen gas tubes as light source. Since the gas in the tube is the molecule $H_2$ , why we obtain the spectrum of atomic hydrogen? My guess ...
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25 views

vacuum pack of a substance/substrates

What equipment can I put a substance or substrate under vacuum pack? After buying this SERS silver substrates (which can rapidly decay in air). I need to immediately put them in vacuum packaging or ...
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42 views

Mass spectrum peak at 40 amu? [closed]

I am using a quadruple mass spectrometer to measure various compositions. First, I did it with air and found the main peaks of $\ce{H2, H2O, N2, O2,}$ and $\ce{CO2}$. Then I added isopropyl alcohol to ...
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1answer
36 views

Will Raman photon counts/Spectral resolution increase if laser beam becomes parallel? [closed]

Most Raman spectrometer has the laser converging into focus with the sample at center like this. Usually how many millions of H2O atoms will be covered by one spot size? What will happen if the laser ...
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1answer
255 views

Mechanistic Explanation of Circular Dichroism

I'm wondering if someone can give me a physically motivated reason for why chiral molecules interact with left and right circularly polarized light (LCP) (RCP) differently. Particularly, a quantum ...
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2answers
904 views

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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What kind of Rubber is in the baby teether toy?

Here it says "Made of Environment Friendly Rubber Material. It is 100% safe and non-toxic for baby". It is used by thousands of babies worldwide. But what exact rubber is it chemical wise? ...
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34 views

IR active and inactive C-H stretching

I have two molecules, ethane (CH3-CH3) and 1,1,1-Trichloroethane (CH3-CCl3) and I need to determine if the C-H stretching vibrations for both molecules lead to a net change in dipole moment, and would ...
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45 views

Why do molecules showing a pure rotational spectra require a permanent dipole?

I understand that pure rotational spectra only exist for molecules which have a permanent dipole moment. The common explanation is "so that they can interact with the E-field of the incoming ...
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29 views

Finding wavelength of the centre of Stokes Ro-vibrational spectrum

I have the following rovibrational Raman spectrum for $N_2$: and I am trying to calculate the "wavelength where the centre of the Stokes ro-vibrational spectrum would be observed" if the $...
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36 views

Can you do SERS without a Raman microscope?

Surface-enhanced Raman spectroscopy or surface-enhanced Raman scattering (SERS) is a surface-sensitive technique that enhances Raman scattering by molecules adsorbed on rough metal surfaces or by ...
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What plastic is this? (Raman scan)

I can't recognize the Raman spectrum of this plastic. It's not in the common plastics raman spectrum. It is plastic adaptor for connecting sediment filters. Anyone got idea or recognize what kind of ...
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4answers
1k views

Is it safe to look at a mercury gas discharge tube? [closed]

As part of a chemistry course, I recently observed a demonstration in which the instructor electrified a mercury gas discharge tube (the tube looked something like this image). The glow from the tube ...
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30 views

1,5-Pentanediol MS

I'm having troubles assigning the signals m/z = 41 and 56 of the compound 1,5 pentanediol. I tried the basic fragmentations (McLafferty, loss of OH radical, etc.) but I can't figure the structure of ...
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20 views

How can I cluster infrared spectra?

This is sorta a cross-post from my post in StackOverflow. Although, rather than seeking help with the code I'm here asking for help with a chemical/statistical problem associated with the code. I'm ...
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2answers
60 views

Raman signal of black matte object

This is the raman spectrum of the black cap: I was expecting it to be Polypropylene but the peaks didn't match in wave numbers. Anyone got idea what kind of plastic has that peaks on the side of 1500?...
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1answer
7k views

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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19 views

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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0answers
20 views

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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1answer
39 views

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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1answer
31 views

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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0answers
27 views

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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2answers
66 views

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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32 views

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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0answers
15 views

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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17 views

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 ...
2
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1answer
61 views

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
132 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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1answer
28 views

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. ...
2
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1answer
112 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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14 views

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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48 views

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
522 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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0answers
31 views

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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1answer
41 views

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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52 views

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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30 views

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 ...
3
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1answer
77 views

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 ...
12
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1answer
1k views

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
107 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 ...
2
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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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0answers
31 views

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
69 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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0answers
37 views

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
74 views

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 ...
2
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1answer
88 views

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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