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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What are good, reliable databases of atomic spectra?
I am looking for a database of atomic spectra, which contains
atomic levels and their energies, electronic configurations, angular-momentum characteristics and lifetimes, and
atomic transitions and ...
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0answers
11 views
Path loss in the terahertz band [on hold]
I am trying to plot the path loss in free space versus the frequency. So I need the absorption coefficient of each molecule existing in the air since some molecules absorbs the wave at certain ...
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1answer
14 views
Principle of Energy Dispersive x-ray Spectroscopy
I have a question about the EDS
I don't understand how the detector can differentiate the Energy of incident x-ray simultaneously.
In my thought, the emitted x-ray from the sample have different ...
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1answer
15 views
Why sample is placed after the interferometer in FTIR?
In all image of schematics of FTIR I found (Wikipedia for example), the sample is placed after the interferometer:
Wouldn't this miss some emergent effects, such photo-induced absorption, since the ...
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21 views
Energy dispersive x-ray spectroscopy of H and He
I have read (e.g. here) that you cannot see hydrogen in Energy Dispersive X-Ray (EDX) spectroscopy spectra because it doesn't have a K-shell. To my mind, even if the element is participating in ...
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DIY IR spectrometry - stray light (higher orders diffraction maxima)
Context: homemade IR spectrometer with diffraction grating.
Since
$$m \lambda = d \sin \Theta _{m}$$
diffraction maxima of higher orders from shorter wavelengths will be mixed with lower order ...
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11 views
Crude spectrometer using the Huawei P20 monochrome sensor
I am thinking of taking advantage of the Huawei P20 Leica monochrome sensor to create a crude spectrometer to measure the spectrum of different light bulbs.
I prefer not to use the optical ...
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1answer
64 views
Why do objects have a Natural Frequency? [closed]
Why should an object even have a natural frequency, why not vibrate at any other frequency? This just sounds nonsensical.
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Degeneracy of Polyatomic Molecules
I was given the following question to calculate in a problem class earlier this week:
A volatile pure liquid comprising a single polyatomic molecule is placed in a sealed sample cell in an FTIR ...
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1answer
17 views
Change in vibrionic energy in at atom at a higher excited electron state
I was studying the coupling of Vibrational and Electronic energies and was left confused at one aspect of the subject.
Consider the image showing a transition from one electronic state to a higher ...
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Confusion regarding the possible term symbols/spectroscopic terms for (2p)(3p) configuration
Note: I have read this answer but it still doesn't address my question in terms of the permitted symmetry.
I am learning about atomic states, and possible electron configurations. The first example ...
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44 views
Is there any evidence that 'anthropogenic climate change' greenhouse radiative models describe real atmospheric processes?
The radiative models used by the IPCC predict in case of a doubling of the preindustrial CO2 concentration of 285 ppm in the atmosphere - the current value is 405 ppm - an increase in backradiation or ...
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Relative strengths of multipole contributions in atom photo-excitations
I have heard and read many times that dipole contribution to the photo-absorption matrix element is orders of magnitude stronger than quadrupole. To be exact, they are related as:
$\frac{\langle ...
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1answer
26 views
Vibrational and rotational spectroscopy
I don't understand why vibrational spectroscopy only has 1 intense absorption peak whereas the rotational spectroscopy has many separate peaks and the distance between the peaks is equal. $\Delta E\...
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2answers
24 views
Variation of electronic energy levels $E_{nl}$ of a many-electron with $n$ and $l$
Within the central field approximation, the electronic energy levels $E_{nl}$ depend on both $n$ and $l$.
For a given value of $n$, $E_{nl}$ increases with increasing value of
$l$.
For a given ...
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0answers
134 views
Is there a difference in the infrared absorption spectrum of a greenhouse gas when pure and when mixed with non-greenhouse gases?
According to the standard IPCC greenhouse climate change hypothesis a doubling of the preindustrial CO2 concentration of 285 ppm in the atmosphere - the current value is 405 ppm - would lead to an ...
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1answer
34 views
Frequency gap between neighbouring spectral lines
According to classical theory the atomic line spectra are discrete and their frequencies quantized.
Have the newer quantum theories changed anything since then, giving some other expressions for the ...
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1answer
18 views
Momentum Conservation for ARPES
I have a question about the principle of momentum conservation the modeling of ARPES:
https://en.wikipedia.org/wiki/Angle-resolved_photoemission_spectroscopy#Theory
We split the initial momentum of ...
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1answer
27 views
Which transparent material alters light the least?
I am making a spectrometer as my school project. It's main application will be analyzing the light emitted by various light sources. It measures visible, near IR and UVA/UVB radiation. I need it to be ...
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1answer
34 views
Determination of the variability of different spectra over shorter wavelength ranges from that of a single spectrum?
To pictographically explain, how do you convert Fig. 1 to Fig. 2?
Fig. 1
to
Fig. 2
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2answers
81 views
Why are there so many different “colors” in the line spectra of simple elements?
I understand that atoms emit photons of wavelength $\lambda$ when electrons transition to lower orbitals according to the equation $E = \frac{hc}{\lambda}$. Based on my understanding, those orbitals ...
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18 views
How to find all the possible spectral term for an atom configuration using LS coupling in the case of two unfilled subshells?
I'm not sure how to find all the possible spectral terms for an atom configuration where there are two shells not completely filled or empty.
Here the LS coupling is described for 2 electrons in 2 ...
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1answer
49 views
“For every line in absorption spectra, the corresponding emission line is present, but the reverse is not true”
I was studying atomic physics and read the line
for every line in absorption spectra, the corresponding emission line is present, but the reverse is not true
and I am not able to understand it ...
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1answer
20 views
how to estimate the error of FTIR spectra?
how to estimate the error of FTIR spectra in transmission, especially on the wavenumber ? please
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21 views
Why can't there be a direct absorption of a photon between Raman active states?
My question pertains to the fundamental difference between Raman spectroscopy and IR spectroscopy. Simply put, the Raman active transitions correspond to a change in the polarizability of the molecule ...
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1answer
30 views
In a frequency comb, how is $n$ determined?
A frequency comb from a mode-locked laser produces a series of spectral lines with $f_n = nf_r + f_{ce}.$
$f_r$ is the frequency of pulses coming out of the laser and can be measured directly via an ...
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31 views
A problem in spectroscopy [closed]
In this problem the wavelengths of emission are not equispaced. The answer is given as rigid rotator. We can write the energy as E=BJ(J+1) where J=0,1,2 etc. In order to justify the answer as rigid ...
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2answers
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Can we see emission lines in stars?
I read that stars show both absorption and emission lines. While how we see absorption lines is clear to me, I don't understand how (and when) we see the emission lines. Based on what I read in ...
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1answer
46 views
How to measure width of a very narrow spectral peak without expensive instruments?
Lasers typically have very narrow peaks in their spectrum, much narrower than 1 nm. It would require quite a high-resolution spectrometer to measure such a peak precisely. But if I simply need to find ...
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3answers
72 views
Why would gamma spectroscopy be a tool for nuclei?
I am very much familiar with Atomic spectroscopy, not much with nuclear spectroscopy.
In atoms (electronic cloud), we have electromagnetic interaction that plays the leading role, whose exchange ...
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0answers
45 views
Can you use a pringles can spectrometer for identifying chemicals
There's a lot of designs over the years that I've seen for making simple spectrometers, but I've never seen them tested much beyond pointing them at the different light bulbs in the lab... Here is an ...
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0answers
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Interpreting and correcting negative vertical column densities of a trace gas in the atmosphere
I have a direct-sun spectrometer that I am using to measure the concentration of a trace gas in the atmosphere. The basis of deriving this concentration is the Lambert-Beer's law. Since my instrument ...
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1answer
37 views
A question on the colours of the hydrogen spectrum
Why does hydrogen have 4 lines in the atomic spectroscopy and not more?
I mean when an electron get excited it has more than 4 possible ways to return to the ground state. So why we see only 4 lines?...
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2answers
38 views
Absolute measure of activity
I am generally quite stuck and not sure what the absolute measure of activity is, and relating to my data is more confusing.
So I am trying to calculate the absolute measure of activity of a caesium ...
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1answer
40 views
List of Gamma Ray Spectrum Values
I am trying to identify the peak which is occurring in my caesium 137 spectroscopy graph, and trying to find a creditable source with a list of most if not all gamma decay spectrum values for all ...
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Difference between X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) [closed]
What are differences between X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) in terms of application and reliability?
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1answer
26 views
Composition of bubbles in glass products
I have noticed that some glass products hold small bubbles inside them:
Since the process by which these pieces are produced (forming) is unlikely to introduce air bubbles, I'm assuming that these ...
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1answer
77 views
How in Cesium 137 spectroscopy Barium X-rays being detected?
Iv been looking at gamma ray spectroscopy of late for a project that I am currently researching and going to be doing in the lab, but what I cannot seem to figure is how the barium x-rays are being ...
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1answer
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Gamma ray spectroscopy lab experiment : Cobolt 60 Data
I am currently carrying out an a gamma ray spectroscopy experiment. At this moment in time I am trying to decipher what parts of the gamma spectrum are what, i.e Compton edge, backscatter, photo peaks ...
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1answer
60 views
Is it possible to simulate Diffuse Interstellar Bands?
I recently saw this YouTube video about Diffuse Interstellar Bands (DIB) which describes the confirmation of a buckminsterfullerene as the source of one DIB.
Is it possible to simulate how a proposed ...
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0answers
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Photoreactivity/photofragmentation dependence on pressure
Most of the photofragmentation studies I see are done in vacuum or lower pressure. Is this just because of the experimental limitations or the photofragmentation doesn't matter the surrounding ...
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1answer
81 views
What would measuring the position of an electron in an electronic superposition look like?
In view of the Copenhagen interpretation, the state:
$$\Psi = \frac{1}{\sqrt{2}}|0⟩ + \frac{1}{\sqrt{2}}|1⟩$$
is interpreted as "when the system is measured, you have a 50% chance of finding the ...
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1answer
23 views
How do scintillation detectors work, for gamma ray spectroscopy
So I understand what happens in the crystal with respect to the interactions and how the electrons in PMT are multiplied by hitting dynodes etc. But what I can't really seem to find any information on ...
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1answer
42 views
Gamma Ray Spectroscopy-What Happens With Inside the Scintillation Crystal
I am going to carrying out an investigation in the lab on gamma ray spectroscopy and to help me understand the graphs that will be displayed to me, I am researching on the types of interactions that ...
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1answer
27 views
Selection Rules for RF and microwave transition
Consider we want coupling between two hyperfine levels both in the ground state of 87Rb atom. Is the dipole transition rules still valid if we use RF or microwave?
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2answers
95 views
Common materials that reflect and absorb near infrared radiation
Recently I got into an infrared (IR) photography using a modified DSLR in which the IR cut filter in front of the camera sensor has been removed. According to astrosurf.com the usual sensitivity of ...
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1answer
34 views
Spectral widths with increasing central wavelength
One can define an electromagnetic pulse numerically through a field with a Gaussian temporal profile, $$E(t) = E_0\cos(\omega t)\exp(-t^2/t_p^2)$$
Here $E_0$ is the peak field, $\omega$ is the ...
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1answer
168 views
Clebsch-Gordon Coefficient Recursion Derivation
I've got a question regarding a very particular recursion relation that Condon and Shortley use in their book "The Theory of Atomic Spectra," (TAS) which Racah then uses to derive the algebraic form ...
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4answers
147 views
Can Fourier transform be applied to light, as a way to find the individual elements of a color?
The Fourier transform can help one discern the individual frequencies of a sound. Every sound can be decomposed into sine waves.
Knowing that light is a wave, that it "has" a frequency, is it ...
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2answers
60 views
Colors of the Aurora
I've seen several web pages that attempt to explain the colours of the aurora but they seem to gloss over or leave out certain details, so I'm still confused. For example, this page explains it in ...
