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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3
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1answer
490 views

Unequal ionization energies of methane

Why does methane have two different ionization potentials? How does this work? I understand that MO theory predicts C-H bonds of differing strength, while hybridization predicts C-H bonds of varying ...
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1answer
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Is trans-2-butene IR active with regard to its C=C bond?

To be IR active, the vibration of a bond must result in a substantial change in dipole moment. Since trans-2-butene is symmetrical, will the C=C stretch show up on IR? Something tells me no because ...
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Resonance contributors and IR stretching frequency

I am told that a carboxylic ester would have a higher carbonyl stretching wave number than a carboxylic amide due to there being more double bond character in the carbonyl group of the ester. This ...
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1answer
1k views

UV-VIS spectra of n-decanes

I was wondering if anyone knows where I can find UV-VIS spectra of the n-decanes. Specifically tetradecane and dodecane. I can't seem to find such information using my regular search methods, so I ...
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1answer
846 views

Interpreting the Infrared Spectroscopy(IR)?

I have already attempted to interpret some of the peaks. Please tell me if they are correct/incorrect and anything that I have missed. Thanks !
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1answer
1k views

Interpretation of the following IR?

I have the following IR Spectrum that I am trying to interpret: So far I am thinking this compound have: a primary amine due to two peaks at 3624 and 3533. The sharp peak 3416 could indicate an ...
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1answer
214 views

What causes Copper Rose?

We made a solution of Tetrakis Copper(I) hexafluorophosphate and the usual color is yellowish. As it oxidizes to Cu(II), it should turn blue. However, our current mixture has an off color that is ...
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1answer
1k views

Information depth in x-ray photoelectron spectroscopy (XPS)

What is 'information depth' in XPS and what does determine it? Also how does it depend on the 'take-off angle'?
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1answer
68 views

Atmopsheric Gas IR-Spectra

I am looking for normal resolution IR-spectra of: $\ce{O2}$ and $\ce{N2}$ at high concentrations and; common minor gas in atmosphere: $\ce{H2O}$, $\ce{CO}$, and $\ce{CO2}$ at environmental ...
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2answers
11k views

light Intensity and its effects on energy and emitted electron on metal surface

we have a metal surface with electrons in a specific energy state say X ,now we shine light on it of specific wavelength and intensity. now what if i double the intensity of light , what would happen ...
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1answer
143 views

What are some incapabilities that the early spectroscopy have when compared to the more modern method?

What are some incapabilities that the earlier spectroscopy (Visible, Ultraviolet and Infra-red) have when compared to the more modern method?
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238 views

How could a scientist from the 1800s to the 1920s run spectroscopy of chemicals?

How would such a scientist be able to get the spectroscopy of chemicals? Without access to modern computing or electronics how would it be possible? Any video link or reference link are much ...
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1answer
14k views

How to calculate m/e value for the base peak in mass spectroscopy?

My working out: Propan-1-ol : CH3CH2CH2OH This can be broken up into: CH3 + CH2CH2OH CH3CH2 + CH2OH CH3CH2CH2 + OH Base peak = most abundant fragment formed (highest peak) How do i know which ...
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2answers
166 views

What is the process involved in performing a mass spectrometry experiment?

I have heard that mass spectrometry is very time consuming: why is this? What is the process involved in performing a mass spectrometry experiment? What steps are the most time consuming?
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35k views

Difference between an absorbance, emission, and excitation spectrum for uv-visible spectroscopy

The exam paper answer is 500, because we need the wavelength of "maximum absorbance." But this graph shows two curves, and the absorbance curve is omitted. But what is the difference between an ...
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2answers
1k views

1H-NMR and deducing structures

here is the data booklet we must refer too: Here is the exam paper solution: I dont understand how they conclude this. Peak areas and the chemical shifts seem to be different for me. For example ...
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1answer
6k views

UV-Visible Spectroscopy in the analysis of sodium chloride in potato chips

Here is the question and answer out of an exam paper: Firstly, I thought UV-Visible can also use radiation in the visible spectrum. Also when analyzing sodium chloride (a molecule), then UV-Visible ...
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2answers
283 views

Fluorescence Spectra, emission spectrum

What exactly does the excitation spectrum tell us about a sample in Florescence Spectroscopy, what information does it tell us? I know that we will get an output of concentration vs intensity but that'...
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1answer
12k views

What is the bandgap value of SiO2?

Using Diffuse Reflectance Spectroscopy, I have obtained the band gap for $\small\ce{SiO2}$ (purchased from a chemical retailer) in the range of 3.25 to 4.75 eV. I would like to know if the values ...
3
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1answer
606 views

Looking for raw interferogram data / raw FID data from FT-IR / FT-NIR / FT-NMR

I'm trying to get my hands on some raw interferogram data / raw FID data from an FT-IR / FT-NIR / FT-NMR so I can run some tests using FFT with it (it needs to be real data). Here's a picture below of ...
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0answers
184 views

How to get defect-energy level diagram from PL data

I am reading this article Phys. Chem. Chem. Phys. , 2011, 13, 14902-14905 and seen that the authors have drawn a image of defect level using PL data Can you explain me how this diagram can be drawn ...
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2answers
530 views

Does my data show quadratic regression in a calibration curve?

This data was taken for my science fair project, and I would like to know the relationship between spectrophotometer absorbance and cell density (taken manually) of algae after a toxicity test. The ...
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1answer
117 views

Are there any molecules with the same spectrum?

Are there any two distinct types of atom or molecule that have identical emission or absorption spectra?
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1answer
211 views

Changes in defects in a material due to heat treatment

Currently i am doing some research on optical properties of a oxide material and for that purpose i have done some photoluminescence study on it. Because this is an ongoing research i cant divulge ...
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1answer
2k views

Extracting elemental ratios from X-ray photoelectron spectroscopy (XPS)

Is it possible to extract information on elemental ratios from X-ray photoelectron spectroscopy (XPS)? For example, I am reading a paper and in it they say that the carbon to oxygen (C:O) ratios of ...
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1answer
25k views

What is the principle of diffuse reflectance spectroscopy behind band gap measurement?

As the title suggest can you explain how DRS can be used for finding band gap of a material. Below is an DRS output result: From the figure we can see that at about 465 nm the reflectance drops ...
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1answer
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Wavelength of light

how do you calculate the wavelength of light? For chemsitry lab, we calibrated the scale reading of Hg, for example, to be 4.91 cm which is violet and the given wavelength says 436. For Hg, it says ...
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1answer
2k views

Can dust or fingerprints interfere in ultra-violet spectroscopy

My question pertains generally to any form of spectroscopy, but I'll focus on UV spectroscopy. I am trying to get information on carrying out spectroscopy, but most of it is theoretical. Wikipedia is ...
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1answer
272 views

What does the signals in a XPS spectrum mean?

I was trying to figure out the different peaks in a XPS spectrum for Molybdenum, but I could not understand them. About XPS, I know that this technique is based on the binding energy of the electrons ...
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1answer
3k views

How do I know if concentration of Ammonia affected my absorbency measurements?

This is for determination of copper in a penny Lab. After making standard solutions we made a solution with a penny, dissolving it in nitric acid and adding ammonium hydroxide to form a more ...
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1answer
1k views

Explanation of the Selection rule in light of IR spectroscopy

I am in mathematics, but I am writing a paper on molecular vibrations (because you can use representation theory to handle this). I want to prove the selection-rule, but I also have to give a ...
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2answers
3k views

How much CO₂ should one expect in an IR spectrum?

I ran an IR spectrum ($\ce{KBr}$ pellet) and found a sharp absorbance at $2360 \text{cm}^{-1}$, which was unexpected. As far as I can tell, this indicates either a nitrile or $\ce{CO2}$. I know that ...
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2answers
2k views

Can ammonia be detected by a 1D-1H-NOESY experiment?

I'm not detecting ammonia in my samples while using a NOESY pulse program for a 1H-NMR experiment. Is it possible for ammonia to be detected by a 1D-1H-NOESY experiment?
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1answer
249 views

Fourier transform for spectroscopy spectra?

I was thinking back to my chemistry major days and remembering the bunch of cool spectra we produced by various means (HNMR, IR, UV/Vis) and I remember all the cool 'self-interference' like couplets, ...
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2answers
13k views

Temperature dependence in absorption spectroscopy

What are some qualitative guidelines one should know regarding the temperature dependencies (of the gas and maybe the radiation, if that makes sense) for an absorption spectroscopy measurement? How ...
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1answer
763 views

When simulating spectral line broadening, which convolution is preferred?

Many computational chemistry packages permit the calculation of vibrational and electronic spectra. These spectra are obtained as a set of discrete eigenvalues however they are often convolved with ...

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