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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How to calculate concentration of trace metal? [closed]

How to calculate concentration of heavy metal in ppm using calibration curve and standard addition method?
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16 views

Finding the thermodynamics of protein unfolding from temperature and absorbance using fluorescence spectroscopy?

I recently did an experiment on protein unfolding using a Perkin Elmer fluorescence spectrometer. The protein was $\alpha$-chymotrypsin. I was given this paper for my procedure. I am now trying to ...
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15 views

Echelle Monochromators

"For any given order, the wavelength dispersion is approximately linear. but the dispersion is relatively small at lower orders or higher wavelengths." As you can see, wavelength dispersion and ...
2
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1answer
35 views

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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1answer
33 views

Where can I find the infrared band positions for phosphorus compounds?

I am trying to interpret an IR spectrum where I have $\ce{(NPCl2)3}$ I have $\ce{P-N}$, $\ce{P=N}$ and $\ce{P-Cl}$ bonds and it is cyclic. Where can I find or does anyone know what the general ...
2
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1answer
22 views

How is 2D spectroscopy able to show quantum coherent transport through networks?

For wave-like (quantum coherent) energy transfer in networks (eg. propagation of excitation in photosynthetic protein complexes of algae or FMO complex in plants) 2D electronic (photon echo?) ...
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1answer
82 views

Why is there a doublet instead of a singlet in this Wittig reaction salt configuration NMR?

I did an NMR sample to my salt p-carboxybenzyl triphenylphosphonium bromide. I got a doublet at 5.26, and according to every article it belongs to the $CH_2$ next to $P^+$, but how come I didn't get a ...
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1answer
31 views

Why are square planar coordination compounds with four different ligands optically inactive?

Why square planar co- ordination compounds of type Mabcd do not show optical activity, although they contain 4 different ligands ( i.e. chiral central metal atom)
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1answer
12 views

How can we measure electronic excitation in some “nm”(nanometres)?

I have no idea to which concept this belongs: The widest range over which electronic excitations in organic compounds occur, is A) 200 nm – 780 nm B) 220 nm– 500nm C) 250 nm– 700 ...
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39 views

Which vibrational modes of CO2 and CSO do not lead to IR absorption bands?

I recently came across this question, I have no idea about IR: Which of the following vibrational modes show no IR absorption bands? A) Symmetric CO2 stretch B) Antisymmetric CO2 ...
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20 views

Cation exchange capacity via IR spectroscopy? Is it as good as barium exchange? What is the intutition on how it works?

Cation exchange capacity is often regarded as the single best summary statistic for soil fertility. Years ago, I learned how to measure it myself, in a soil lab. I used compulsive barium exchange, ...
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17 views

Assign symmetric and antisymmetric stetches in IR spectroscopy

Typically the antisymmetric stretch in IR spectroscopy is higher than the symmetric stretch for a given functional group. For example for NO2 the antisymmetric stretch falls at ~1530 cm-1 compared to ...
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11 views

Raman Depolarization Ratio

What is the Raman depolarization ratio? What is a depolarized band, and what does it corresponds to in the structure of a molecule?
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21 views

General methods of Analysis for FTIR Results

What can we say about a molecule from the position and number of bands in FTIR spectrum. I know that the more symmetric a molecule is, the less number of bands it has. What else can we say, for ...
2
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1answer
29 views

Factors to consider to predict EPR

What are the factors to consider when predicting the EPR spectrum of $\ce{Cu(Ox)P(CH3)3}$ where $\ce{OX}$ is the oxalate ion? I understand that there are several factors to consider for EPR (Electron ...
2
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2answers
20 views

Optical Density numbers

If it's OD of 600nm I know that's the wavelength used, but what are the other numbers in something like "OD 600nm of 0.6-0.7". The 0.6-0.7?
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1answer
164 views

Is carbon dioxide IR inactive?

I am told that carbon dioxide is IR inactive. This somehow strikes me as untrue or at best oversimplified, because yes, it is overall symmetrical, but can't $\ce{CO2}$ be induced to show asymmetric ...
5
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1answer
134 views

Interpretation of TD-DFT results

For the first time I'm doing TD-DFT calculations (wB97XD functional) in Gaussian 09 for an open-shell system and the results look like the hell of a mess for me. The molecule is rather big, so I ...
5
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1answer
171 views

How can I deduce the linearity of XeF2 from the IR spectrum?

The vibrational modes of $\ce{XeF2}$ are at $555$, $515$, and $213~\mathrm{cm^{-1}}$ but only two are IR active. Explain why this is consistent with $\ce{XeF2}$ having a linear structure. From what ...
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1answer
96 views

HNMR Assignment

I have a molecule and i need to assign the hnmr. I have a printed spectrum So far my answer is: chemical shift_______splitting pattern_______coupling constant ...
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2answers
216 views

What splitting pattern is this?

I am trying to find the structure of an unknown molecule. What is the splitting pattern of these sets of lines? I think my unknown molecule is butanol and the hydrogens this splitting pattern is ...
6
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3answers
167 views

Nanoscopy Nobel Prize - why are all the tools in the visible light range?

It seems like all the new advances in molecular imaging/microscopy are in the visible light range of the EM spectrum. An example would be the most recent Nobel Prize for Chemistry. Is there some ...
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1answer
192 views

Proton NMR signals and rings

Does pyridine or furan have the more shielded proton NMR signals? I know that both are aromatic, so both have rather deshielded signals due to ring current combining constructively with the applied ...
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1answer
54 views

Chemdoodle to mestranova

Is it possible to copy my chemdoodle displayed structure into mestranovea? I have tried simple dragging (mac) and all the various copy/paste options... any ideas?
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1answer
296 views

How does different diffraction grating effect resolution and sharpness of lines in a line spectrum?

In my lab notebook it asks us to think about the spectroscope further than the reading goes on. It asks if we use a diffraction grating that contains 600 lines/mm in the spectroscope what do we ...
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1answer
52 views

13C NMR peak location in butanone

The above is the correct $ ^{13}C $ NMR spectrum of butanone. In the $ ^{13}C $ NMR spectrum of butanone, I figure that the peak locations of the first and third carbons should be switched (27.3, ...
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1answer
50 views

Do acyl fluorides exhibit resonance donation or inductive withdrawal?

I know that in acyl chlorides, there is partial triple bond character in the C=O bond not because the chlorine is electronically donating (due to size mismatch with carbon) but because the chlorine is ...
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1answer
44 views

What is the product of two irreducible representations on the character table?

Let's say the direct product of $\ce{A1}$ and $\ce{B1}$ on $\ce{C}_{2v}$ character table, what is the direct product of the two for water molecule? or for any other instance in general, what does the ...
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1answer
44 views

Using MestReNova: An Introduction

Can anyone help me with a quick question regarding MestReNova 9.0. I have been fiddling with this thing all day and before you ask yes, I have consulted the users guide to no avail. I want to do ...
3
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1answer
134 views

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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18 views

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 ...
3
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1answer
85 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 ...
3
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1answer
231 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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95 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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1answer
41 views

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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1answer
89 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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1answer
74 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
129 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 ...
2
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1answer
153 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 ...
3
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1answer
43 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
149 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 ...
3
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2answers
218 views

How do I find out what benzene containing compound this is with IR and NMR?

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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3answers
290 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 ...
2
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1answer
106 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
80 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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30 views

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 ...
2
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25 views

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 ...
6
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1answer
156 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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1answer
94 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
218 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 ...