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Questions tagged [spectroscopy]

the practice of separating a signal by frequency (or sometimes energy or momentum) and analyzing the resulting spectrum.

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17 views

Units in Representation Of Energy Density Spectrum

In most of the texts, I referred to The Axis being labelled with Units as shown above. But I also found few images with different Notation (1/Units) Being Followed as shown Below. The units of the ...
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Why is elastic scattering of photons (largely) non-isotropic, but inelastic scattering is isotropic?

I'm working on an experiment regarding Raman spectroscopy, and i'd like to fully understand the reasoning behind this fact. I assume it is related to the photons momentum. My apparatus has a '...
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39 views

NMR spectroscopy

I was wondering how many times larger is the magnetic moment of an electron compared to a proton? How come the electrons magnetic moment play no role in NMR and MRI? Edit Electron Spin Spectroscopy ...
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65 views

Completely forbidden transitions

$\newcommand{\bra}[1] {\left< #1 \right|} \newcommand{\ket}[1] {\left| #1 \right>} $In molecular physics and spectroscopy physicists often calculate the dipole transition elements between two ...
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28 views

Different wavelengths effect on matter [on hold]

The figure covers xrays and up, UV, Visible, Infrared and Microwave. But what about lower wavelengths like ELF and radiowaves in the 20-900 MHz range? There are conspiracies regarding ELF and HAARP ...
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82 views

Why is blackbody radiation continuous?

I will preface this by saying I am not a physicist and have not taken a course on spectroscopy but I had some basic questions as I work with IR spectroscopy. Is it accurate that photons are only ...
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Do rainbows show spectral lines from the sun?

I'm aware of a similar question being asked in Do rainbow shows spectral lines?: The response to this question is that the body producing the light is not the water droplet that merely diffracts it ...
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44 views

Why can't all spectral lines be seen through a spectroscope?

We did a lab where we looked at heated hydrogen, helium, argon, and neon gas through a handheld spectroscope. We had to track the colors of each line on a separate paper. However, for the argon, and ...
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1answer
16 views

Multiple wavelength peaks in HeNe spectrum from FTIR

I recently used a Michelson interferometer the find the spectrum of a helium neon laser. Initially, I moved the mirror $9\times10^{-6}m$ and the spectrum was as expected, single peak at approx. 633nm. ...
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38 views

What is Fermi Surface of superconductors?

It is known that, in superconductors, at the Fermi level, electrons are paired(Cooper pairs) and there is a gap (see figure). However, there are lots of ARPES experiments showing the "Fermi surface" ...
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28 views

Interpretation of the photon scattering rate?

The photon scattering rate $\Gamma$ describes the rate at which photons scatter off an atom$^1$. In a two-level system, the ansatz for the photon scattering rate often is given by \begin{equation} \...
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28 views

How to interpret stretching mode between two atoms in solid-state crystals?

I have a fundamental question about the definition of "stretching mode" obtained from molecular dynamics simulations. Is it the fourier transform of autocorrelation of bond lengths over a time period ...
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S-W correlation plot from positron annihilation Doppler broadening spectroscopy

From Doppler broadening spectroscopy, we get the S-parameter and W-parameter. I found a S-W correlation plot in many research papers. What information does this plot provide?
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40 views

Black body radiation and line spectra

Firstly, Blackbody radiation and line spectra are both a phenomenon of energy emitted(EM), but why is the blackbody radiation spectrum continuous while line spectra is not continuous? Secondly, ...
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67 views

How is a spectrometer is calibrated for intensity?

For the case of spectrophotometers, we can easily calibrate the device(intensity wise) taking the light source inside the device as the reference, without any need of precise knowledge about its ...
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32 views

Does the spectrum of two-beam interference also show an interference pattern?

I know when you interfere two beams you get an interference pattern with a fringe pattern of λ/(2*sin(θ/2)) in physical space. It seems that there must also be modulation of the spectrum. Is this ...
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Is there a difference in wavelength emission spectra of ZnS:Ag when its irradiated with protons vs. gammas?

How would I measure this, because I couldn't find this information in literature as of yet? I have neutron (to produce protons by recoil) and gamma sources, but I don't have a pure neutron source, and ...
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Electronic transitions between sublevels

Is there any rule that says about electronic transitions between sub energy levels? Example only l =+1 or -1?
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12 views

Fitting Beta Emission spectrum data according to fermi function

I was trying to fit beta emission spectrum data to the equation $$\tau(E_e) \propto (E_e^2 - m_e^2 c^4)(Q-E_e)^2\frac{E/c}{\sqrt{E_e^2 - m_e^2 c^4}}.$$ However, on making a custom equation in Origin,...
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Flame under immense pressure and moderate temperature

Consider the flame inside a rocket engine's pre-burner, where the pressure is truly immense (400~600 bar) but the temperature is quite mild (<1500 K), and the flame is of the premixed type. Under ...
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Taking out % contribution of a zero order state from an eigenvector - dipole calculation

I am doing an analysis of a theoretical spectroscopy calculation. I take an eigenvector (nx1) and dot it with many zero-order dipole vectors (nx3) to get the dipole contribution to my new eigenstate. ...
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Design and construction of a system identifying molecular nitrogen and water

I have read papers that use LIDAR-like and LIDAR-Raman systems that detect elements. I want to measure the vapor water ($\rm H_2O$) and $\rm N_2$ of trees/agriculture using Arduino and low cost ...
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Electronic levels of Cadmium I

I am working on an assignment, and I have ran into a few issues. I tried asking my teacher, but he has been away and is not answering any E-Mails. My problem is as follows:Considering Cadmium with $Z=...
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Difference between electrical conductivity and optical conductivity

Is there any difference between electrical conductivity and optical conductivity? How to explain it physically and is there any method available to connect them mathematically? If I calculate carrier ...
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1answer
31 views

Mass and energy of radiation

We know that mass can be  converted to energy and vice versa. So does the mass of molecules or atoms change when they absorb a radiation and go to the higher energy state?
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Is the integral of the spectral irradiance graph equal to the total energy absorbed?

This image is found on wikipedia: My question is essentially: how can I read from this graph the actual total energy absorbed by the earth? Is it true that the total red area is equal to the solar ...
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Does emission-spectrum of molecule equal sum of emission-spectrum of its components

Imagine a number of elements with known emission-spectra, that form a primary chemical bond of either * ionic * covalent * metallic type. Does the emission-spectrum of the resulting molecule match the ...
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36 views

Radiation Emission in Rotating and Vibrating polar molecules

So, I am currently doing a course in Molecular Spectroscopy and I am finding some concepts very non-intuitive and very difficult to understand(maybe due to lack of my knowledge or the lack of ...
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1answer
60 views

Echelle grating

An echelle spectrometer has one low groove density grating (echelle) and one high groove density grating. https://en.wikipedia.org/wiki/Echelle_grating After the echelle grating there will be many ...
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How can you explain long lifetime of the Rydberg atoms? [duplicate]

Long lifetimes of the Rydberg atoms seems counterintuitive to me. Intuitive explanation: the higher electron was excited, the more levels below became available for spontaneous decay. So the first ...
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147 views

Problem with the derivation of the Doppler broadening of atoms spectral lines

I have a problem with the derivation of the gaussian behavior of the doppler broadening of gas atoms specrtal lines. I will describe what I have done so the problem along the derivation could be ...
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Rebinning experimental data

I am working on a spectroscopy experiment and for each wavelength of a laser I have some counts. For the purpose of my question I will make up some data to illustrate my problem, in the table below (...
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2answers
110 views

Why is the spectrum of a star pretty much continuous? [duplicate]

I was reading about the development of the quantum theory when I got to the explanation for spectral lines. It's a topic that I've revisited many times but I came up with a question. I know that in ...
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How to identify properties of a concave diffraction grating

As a little side project I want to build a spectrometer. The main components are an entrance slit, a concave diffraction grating and a CCD sensor (also the electronics). I bought a used diffraction ...
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Equivalent Width: Strong and weak lines

Equivalent width of lines are known to characterize the overall strength of lines. However, if there are two absorption troughs, with the same equivalent width but different depth, which is possible ...
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Is there a way to precisely measure or infer the color of a material from a distance (~2m)?

I've recently started working on a graphics/SLAM project. I've encountered a problem that requires the measurement or inference of the color / spectral reflectance (and ideally albedo) of points on ...
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19 views

Auger electron spectroscopy

I am doing Auger electron spectroscopy on a sample. I found the differential spectra is not symmetrical. For example, oxygen peak in as received sample looks symmetrical but that for carbon is not ...
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1answer
24 views

Spectrograph difference between cross disperses and echelle gratings?

In echelle spectrographs, the presence of echelle gratings and cross-dispersers is common. What task does each one perform? Why are the cross-dispersers needed?
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Critical Point in Derivative of Absorbance

Background, and Question I have a graph of $\frac{dA}{df}$, change in absorbance, over the change in frequency. I have a $A'= 0$ which happens to line up with a peak in absorbance, and a transmission ...
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High-purity silicon detector vs HPGe for gamma-spectroscopy

Is it possible to construct a high-purity silicon detector for gamma spectroscopy the same way HPGe detectors are made? Will it work when cooled to the same 77 K? Why HPGe is mainly used for gamma ...
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What is absorbance and Transmittance?

I am currently doing some work in Spectroscopy, and I was wondering how are absorbance, and transmittance related? Do they have a domain, and range, how to read some sample graphs. I was ...
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What does represents the concept of “magic wavelength” in optical frequency standards?

I cannot find on the internet references on this topic, so I'm trying to post my question on this forum, this is the first time I post here. I can't understand the difference between "normal" ...
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83 views

Are there names for Helium (He) emission lines like the Lyman/Balmer/Paschen series in Hydrogen?

Just wondering if helium emission lines have names like hydrogen lines. For instance the Balmer series is: $$H_{\alpha}, H_{\beta}, H_{\gamma}, H_{\delta}...$$ The Lyman series is: $$L_{\alpha}, ...
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Relation between oscillator strengths $\log{gf}$ and the Einstein $A$-coefficient, rotational quantum number, …

I'm analyzing the spectra of M dwarfs. Some authors characterize the lines with the oscillator strengths $\log{gf}$ while others follow different paths with the Einstein $A$-coefficient. I would like ...
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29 views

Can a LGL (Lens-Grating-Lens) spectrometer have a non-zero geometry?

I am designing a transmission grating based spectrometer. Can the angle of incidence on the grating (alpha) be unequal to the diffraction angle (beta)? I didn't think that they could be varied as i ...
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324 views

What is the cause for the fine structure?

What is the cause for the fine structure? I know that it describes the splitting of the spectral lines of atoms but I don't understand its cause, any help is appreciated
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Has man ever observed the spectrum of a single hydrogen atom?

Were there this kind of experiment done before? The spectrum we observed is radiated by huge number of hydrogen atoms in the gas, not by single hydrogen atom. I know it's very hard to test a single ...
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Are there accepted spectral lines, or wavelength of light emitted, for the various neural and ionized atoms? If yes, where can I find them? [duplicate]

I am working with the redshift phenomena and analyzing the spectral lines of various emissions by galaxies. However, when I came to analyze the change in wavelength I was confused on what to compare ...
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23 views

Laser power inside a vapour cell

I have a laser beam whose power I measured to be x $\text{mW/cm}^2$. Furthermore, I measured the beam profile of the laser beam and therefore can estimate its intensity. I shine this laser through a ...
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Neutral lithium ionization energy for removing an electron from the $1s$ orbital

How much energy does it take to singly ionize a neutral lithium atom by removing an electron from the $1s$ orbital?