Spectroscopy is the study of the interactions between matter and radiated energy. Experimentally, the results are returned as a function of wavelength versus amplitude (intensity), where the spectral lines represent the resonance frequency of the sample.

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Ring Strain and C=O Stretching Frequency

Why does C=O stretching frequency increase with ring strain? Why does conjugation decrease C=O ring strain? I am told that cyclopropanone exhibits a higher C=O stretching frequency than does ...
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Why does the absorbance of Ca decrease in the presence of certain metals?

I'm trying to find a reason for an experimental observation, I noticed that when the absorbance of $\ce{Ca}$ is measured with FAS(flame atomic spectroscopy) that it decreases when metals such as ...
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127 views

Symmetry labels for orbitals

What are the symmetry labels for the p and d orbitals of $\ce {[PtCl4]^{2-}}$ ? I understand the concept of symmetry labels for molecules. some explanation of how it applies to orbitals would be ...
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62 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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64 views

Why are d-d electronic transitions forbidden and weakly absorbing? Why do they occur at all?

I am unable to understand why d-d electronic transitions are forbidden? Why are they weakly absorbing and apart from that, why do they occur at all?
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33 views

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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how to determine timescale with characterization methods?

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

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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58 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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37 views

Photoelectric Effect in Semiconductors

Is the photoelectric effect possible for semiconductors? I imagine that this might be, if possible, a two-photon process: excitation of an electron from a filled to conductance band, and then on to ...
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48 views

Difference between torsion, out of plane, coplanar and perpendicular bends?

In Infrared spectroscopy, stretches are easily understandable. But, how do I visualize (or conceptually understand) the difference between dihedral (torsions), out of plane bends, coplanar bends, and ...
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41 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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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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153 views

Help with identifying an unknown substance?

I have the following IR and NMR of an unknown substance. Can someone tell me what is a possible structure of the compound or point me in the correct direction. So far I am thinking of a benzene ring ...
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184 views

Identifying an unknown compound(w/ NMR/IR)?

I need some help identifying the following unknown compound. Any suggestions or hints regarding the possible compound would be highly appreciated. So far I am thinking the broad peak on the IR is an ...
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1answer
83 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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39 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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How can I determine/quantify the presence of boron nitride on a metal surface?

We use micron-grade hexagonal boron nitride (hBN) to coat the surface of bullets that are jacketed in gilding metal. This coating is mechanically embedded/plated onto the surface in order to increase ...
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Synthesizing monodisperse PbS quantum dots

For a research project, I am trying to synthesize lead (II) sulfide quantum dots using the method of Li et al.. Basically, I am injecting sulfur dissolved in 1-octadecene into a mixture of PbO, oleic ...
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131 views

How to make approximation of rotational partition function of diatomic linear molecules?

Using the rigid rotor approximation to the level energies, and such other appropriate assumptions, we can approximate rotational partition function, $Q_{\mathrm{rot}}$, of linear molecules as follows: ...
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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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104 views

$\ce{^13}$C NMR of dimethyl 3,4,5,6-tetraphenylphthalate?

I am trying to assign the peaks here to dimethylphenylphatalate but all the benzene rings are throwing me off. All I can get is that the further most signal is the carbonyl carbon (168.71) and the ...
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56 views

Benzaldehyde NMR Question?

Assuming this image is correct, why is the Carbon-3 more deshielded than Carbon-2 and Carbon-1 ? From what I understand, deshielding is the greatest when the Carbon atom is closer to electron ...
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NMR Spectroscopy Question

From my understanding NMR spectroscopy works by analyzing the resonance frequency of each structure around a hydrogen or carbon. Since every structure is unique and has unique resonance frequency it ...
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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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HNMR - Peak Splitting

If you have $\ce{CH3-\color{\red}{CH2}-CH2Br}$ Then the $\ce{CH2}$ (in red) would have a peak splitting of $12$ because $(n+1)(m+1)$ where $n$ for the $\ce{CH3}$ is $(3+1=4)$ and m for $\ce{CH2}$ is ...
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Is visible spectroscopy the only non-electronic method of all the spectroscopy method?

Is visible spectroscopy the only non-electronic method of all the spectroscopy method? I know some of the spectroscopy method is possible being used because of electronics.
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80 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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46 views

How to calculate the rotational constants for different states from a stick spectrum?

Given a stick spectrum for an unknown diatomic molecule, how do you determine the rotational constants $B_\nu$ for both the excited and ground states given that $$E_{j}=B_{\nu}j(j+1)$$
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162 views

Distinguish between symmetric and asymmetric molecules with IR

I get increasingly nervous as I get my organic lab course reports. For, I often get asked whether the peak in the IR comes from an asymmetric or symmetric stretch. I've looked at about ten books and ...
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Why is a singlet state called singlet and a triplet state called triplet?

I kind of get the idea of singlet and triplet states. But why are they called singlet and triplet (what is the single and what is the triple in these cases)? I feel that I am missing something ...
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54 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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87 views

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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86 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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137 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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217 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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70 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 ...
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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 ...
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34 views

If absorbance is 0, what is the equilibrium constant?

If the absorbance of something is 0, what is the equilibrium constant? In a reaction, the absorbance is 0, so the concentration of the product is 0. The concentration of one of the reactants is also ...
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193 views

Why is filter paper fluorescent?

Typical filter paper used in chemistry lab (e.g. Whatman #1) exhibits autofluorescence in near UV with excitation maximum at 365 nm and emission maximum at 440 nm. It was reported in literature1 that ...
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67 views

Alcohol irregularities in Hydrogen NMR

We've started learning about NMR in my ochem class and my instructor told us that in Hydrogen NMR an alcohol can have a fairly wide range of possible values - usually from about 2 to 5. He said that ...
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69 views

Help with understanding term symbols

I think that I understand most of the parts of the symbol shown for ground state oxygen However, I was hoping that someone could tell me what exactly the negative superscript sign means? And how do ...
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102 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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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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106 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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101 views

What is the approximate lifetime of an $S_N2$ transition state complex?

Imagine some $S_N2$ reaction involving an aliphatic $sp^3$ carbon with a halide leaving group (e.g. Iodide or Bromide). Given the rise of femtosecond spectroscopy (e.g. using a mode-locked ...
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209 views

Why does the excitation and emission spectrum of a fluorescent molecule have overlap?

Question is rather self-explanatory. Came up during a lecture without a concrete answer. I understand that the differences in emission wavelengths is due to relaxation to the lowest energy level of ...
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39 views

Red glow in the dark pigments

I want to do some spectrometry experiments with glow in the dark paints. The red paints I've read product details for all seem to require a uv light to charge. Are there any red glow in the dark ...
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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?