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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Why can we eliminate the Doppler-broadened background by chopping the pump beam?
In Wolfgang Demtröder (auth.) - Atoms, Molecules and Photons we have this laser spectroscopic setup.
Without any explanation he claims the chopper can fix the Doppler broadening background shown on ...
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Why solids can produce a continuous light spectrum?
A textbook mentions:
A bulb has a solid filament that is heated. Energy levels in solids overlap, so all energy changes for the electrons are allowed. This means the electrons can emit photons ...
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The typical IR spectrometer broadband source emits all IR frequencies of interest simultaneously
I am currently studying the textbook Infrared and Raman Spectroscopy, 2nd edition, by Peter Larkin. In a section entitled Infrared Absorption Process, the author says the following:
The typical IR ...
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Anomalous Zeeman Effect
I was reading splitting of spectral lines in magnetic field and my book says
In anomalous Zeeman Effect,
Classically, the ratio of orbital angular moment to angular momentum $|\vec{L}|$ gives ...
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Is there a UV-VIS spectral database for common materials?
Looking for a database of spectral data in the ultraviolet to visible range (interested in roughly 200 to 800 nm) for common materials found in homes, vehicles, mass transportation, factories, etc. ...
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Interpretation of the output of a spectrometer: wavelength to energy conversion
First question
This question may be uber-trivial, but I have a spectrometer that provides as output the number of ADC counts at given wavelengths (the wavelength vector is not equally spaced), i.e., ...
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38 views
Is there an authoritative data source for EM spectrum assignments?
I'm working on some software to coalesce various standard constants (eg SI, CODATA, AME) into an easy-access library. However, trying to find an authoritative source I can find for EM spectrum ...
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Analysis of Angle resolved photoemission spectroscopy(ARPES) data
I was reading a thesis on ARPES and it's role. In one place, it was mentioned that ARPES is able to map the whole 4-dimensional momentum energy space for a given material. But to create a full 4-D ...
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In what sense are boron and carbon the simplest examples of degenerate atomic ground states?
According to this accepted answer, the most simple example of two atoms with degenerate ground states are boron and carbon. But hydrogen is the simplest of all which has the ground state configuration ...
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How complex is a spectrograph to design and produce?
I am interested in exploring multi-spectral imaging, particularly in the (mysterious, invisible) near infrared. I have seen that you can turn a monochrome area scan camera of MxN pixels into a multi-...
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1answer
35 views
Does a blue, transparent liquid reflect or transmit blue light?
I've made a very simple colorimeter. An RGB LED illuminates transparent liquid samples with red, then green, then blue light. A detector detects the intensity of light that comes through the liquid.
...
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Will ions in a solution emit radiation from an electric discharge?
If I pump enough current through a water solution with ions in it, will the ions in the solution emit EM radiation as the water heats up to form a "spark"/plasma? Basically trying to make an ...
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Is it possible to probe the molecular vibration of diatomic molecules without a dipole moment by some way?
I was reading about the vibration frequencies of molecules, and I realised molecules like iodine (diatomic) have only 1 vibrational mode, and the vibrations are too weak to be probed. Is it possible ...
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Identification of lines in an electronic spectrum
I'm using PGOPHER to simulate fluorescence spectrum of oxygen (of the transition $^{3}\Sigma^{-}_{u}$,v'=2 - $^{3}\Sigma^{-}_{g}$, v''=0). Even though I have read the description about the line list ...
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Fraunhofer line width
What sets the width of Fraunhofer lines on the solar spectrum ?
I first thought of Doppler broadening, but numerical applications result in much too high temperatures. For instance, using these data,...
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Why do we only see transitions corresponding to circularly polarized light in dichroic spectroscopy?
I'll be using the diagrams here to explain a bit:
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=5393
In dichroic atomic vapor spectroscopy you have a constant longitudinal field through ...
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Simluation of time-resolved fluorescent spectrum
I'm trying to model time-resolved fluorescent spectrum of diatomic molecules. My questions concern some formulas in "Atoms, Molecules and Photons An Introduction to Atomic-, Molecular- and Quantum ...
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1answer
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Decay of an electron not in eigenstate
Suppose the electron of a single electron atom is in the state $ a|{E_{1}}\rangle + b|{E_{2}}\rangle $. If it decays to the ground state $ |E_{0}\rangle $ which spectral lines do I expect to see? The ...
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Velocity distribution for Molecular beam vs. gas
In the book: https://g.co/kgs/JRBLeA (Atomic Physics by C.J. Foot) on page 152 there's a table in the end that compares gas' velocity distribution and that for a molecular beam. I am unable to account ...
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1answer
88 views
Why can atoms only absorb/emit certain frequencies of light?
I'm aware that the orbitals of atoms have discrete energy spectra. The energies must obey the atom's Hamiltonian eigenvalue equation $H|\psi_n\rangle=E_n|\psi_n\rangle$ and this only holds for certain ...
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Inconsistent derivation of Doppler broadening of spectral lines
The following explications are usually made for the derivation of the Doppler broadening of spectral lines as shown in
Foot (2005) Atomic Physics, sec. 8.2 (see below)
Demtröder (2014) Laser ...
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How do you experimentally determine the value of the Compton edge from data?
A NaI scintillation detector was used to acquire the following data. In order to calibrate the detector, I fitted a Gaussian function to the photopeak. I now want to check that my measured value for ...
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1answer
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Understanding the effect of Compton scattering in Gamma ray spectroscopy
The following calibrated gamma ray spectrum was taken using data for a Cs-137 source acquired using an NaI scintillation detector. The predicted value of the Compton edge was calculated using the ...
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Acoustic phonons velocity of GaN
Phonons dispersion is presented at figure below: T. Ruf. “Phonon Dispersion Curves in Wurtzite-Structure GaN Determined by Inelastic X-Ray Scattering”. In: Physical Review Letters 86.5 (2001), pp. 906–...
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Electronic-vibrational-rotational Transition
I'm trying to simulate the fluorescent spectrum for the first time and run into several problems. The dipole matrix element for a transition between 2 different electronic states is as follow:
$$\...
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How do I find the field representation of a light source?
I'm trying to propagate a light source with cross-spectral density
$$W(x_1,x_2)=S_0\delta(x_1-x_2)$$
which is a completely incoherent light source. I want to find the field representation of the ...
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1answer
67 views
Plausibility of detecting viruses using optical spectra [closed]
Ok, this is a huge long shot, and I also apologise if this is a poor question (I'm a newbie here...). This doesn't seem to me a strictly perfect fit for Chemistry.SE, Biology.SE, or Photography.SE ...
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Has anyone tried to find the wavelength to the Corona virus cell? [closed]
I have seen websites and videos that show how cancer cells can be destroyed using sound resonance oscillation. So has anyone heard of anyone who is in the field of sound resonance trying to capture ...
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1answer
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Tips and tricks to improve signal of a low yield sample in FTIR spectroscopy?
I am working on donor spectroscopy in Si. Due to low donor concentration around 10^16 cm-3, the PL signal I get by exciting 670 nm pump is very low, below noise floor. The system is locked-in already. ...
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29 views
Power spectrum on wavelength
For a peak in hydrogen spectrum, we fit a peak function of Lorentzian. I seeked for an explanation and I found the power spectrum $|f(\omega)|^2$ is in fact the Lorentzian. $f(\omega)$ is the Fourier ...
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1answer
23 views
Peak function decision
I am doing a lab of locating hydrogen's spectral lines and peak function fitting is required. It is suggested to use Lorentzian to locate the peaks. I wonder why don't we use Gaussian instead?
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What causes a double peak for a single wavelength when using an optical spectrometer system?
I am doing an experiment to determine the Rydberg constant for the Balmer series using an optical spectrometer system (consisting of a monochromator with a photomultiplier detector and pulse counting ...
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1answer
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How to produce light of a certain wavelength?
Is there a device which takes as input the wavelength or frequency value and produces electromagnetic waves of the given wavelength or frequency using an emitter? It might be that the wavelength range ...
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Förster Theory donor and acceptor spectrum
Why is the absorption spectrum of the acceptor by a lower frequency compared to the emission spectrum of the donor? I expect the the absorption spectrum to be within the same frequency range as that ...
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How to measure thickness of a sunscreen film(nano meters)?
I want to measure the thickness of a sunscreen film. In the current method, I measure the volume of the film and use the area of the substrate to calculate the thickness. But I need a more reliable ...
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Why does an overlap of atomic orbitals in a solid cause a continuous emission spectrum? [duplicate]
A given explanation for a light bulb's continuous spectrum of emitted light was that energy levels in solids overlap, therefore all energy changes can occur.
How can these changes occur? If an ...
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Error in FWHM of photo peak
I have spectra for different sources I need to find the FWHM of to determine energy resolution of a scintillation detector.
I have taken spectra and then fitted a gaussian to the photopeak:
The scipy ...
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1answer
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How to properly calibrate phase axis to represent an optical interferometric stability curve?
Assume we want to measure how stable an interferometer is.
We send two ultrashort pulses (left figure), delayed by the fixed time $\Delta t=T$ relative to each other, into a spectrometer to observe ...
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1answer
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How can we measure thickness of a wet film without destroying it's surface?
I have an opaque(wet) material thin film on a glass plate. How can I measure the thickness of the film without destroying the surface?
I am thinking that I might be able to use a spectroscopic ...
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1answer
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Backscattering of gamma rays due to lead
I am conducting an investigation of backscattering in gamma ray spectroscopy.
A backscattering factor $F_b$ is defined as:
$$ F_b = \frac{N_b}{N_i}\times 100\% $$
where
$N_b =$ Number of photons ...
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1answer
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Why do (semi-)conducting materials absorb microwaves at their cyclotron frequency? - Cyclotron Resonance Technique
I am currently studying third year physics - more specifically a solid state course.
It was mentioned that in order to determine the effective mass of an electron in the nearly-free-electron model ...
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Calculation of atomic spectrum
I need to calculate spectrum of Hg atom (wavelength and transition intensity), taking into account relativistic corrections. Can someone suggest a software or a package for atomic spectroscopy, that I ...
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Looking for papers using pump-probe spectroscopy
I am working on a project explaining the pump-probe spectroscopy, and I need to explain several papers which utilize this technique.
Are there any papers that you would recommend, which are ...
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1answer
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Is it possible to see spectral lines in DVD?
A DVD can split the sun light in several colours as a prism. But is it possible to see spectral lines? I observed sometimes thin dark lines like that in the upper part of the disk. But I'm not sure if ...
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1answer
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Why do satellite methane detectors use some spectral lines and not others?
I was reviewing absorption/transmittance spectra and was wondering why certain wavelengths are chosen for detectors and not others. Take methane for example
For small electronic IR detectors they ...
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Is the plasma frequency independent from the relative dielectric constant of the solid crystal?
I have found many unclear explanations regarding plasma frequency in 3D condensed matter.
Based on many textbooks and Wikipedia, the plasma frequency is
$f_p=(\frac{e^2n}{m*\epsilon_0})^{0.5}/(2\pi)$...
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Is it possible to use a laser to induce a single-species plasma (e.g. Fe)?
I am seeing papers online ([1] and others) that refer to an "Fe plasma" induced by laser. In particular, one uses Nd:YAG on an organic material.
To me, the title implies that a single-species plasma ...
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1answer
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Emission of a “set of discrete frequencies” vs “continuous” emission?
I am reading some notes for a class on computer graphics. In a section introducing concepts such as the pinhole camera model, the author says that light sources can emit light either as a set of ...
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Absorption cross section for Nitrogen in the visible spectrum
I am trying to find data for the absorption cross section of Nitrogen at various wavelengths in the visible spectrum (~400-800 nm).
I can only find data at lower wavelengths, however. Data from the ...
