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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Experimental observation of matter/antimatter in the universe

Ordinary matter and antimatter have the same physical properties when it comes to, for example, spectroscopy. Hydrogen and antihydrogen atoms produce the same spectroscopy when excited, and adsorb the ...
Stefano Borini's user avatar
14 votes
6 answers
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What is the difference between Raman scattering and fluorescence?

What is the difference between Raman scattering and fluorescence? Both phenomena involve the emission of photons shifted in frequency relative to the incident light, because of some energetic ...
Deep Blue's user avatar
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What actually is white light?

I was studying spectra and suddenly a question popped up relating to the absorption spectra. When we say that the electron absorbs certain wavelengths(photons) so we are implying that white light is a ...
chittaranjan rout's user avatar
17 votes
2 answers
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How can we detect antihydrogen?

From a mathematical standpoint (CPT symmetry) it is most probable that antihydrogen has the same spectra (absorption and emission) as hydrogen. The CERN confirmed this hypothesis to a high accuracy ...
dan's user avatar
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Why do lines in atomic spectra have thickness? (Bohr's Model)

Consider the atomic spectrum (absorption) of hydrogen. The Bohr's model postulates that there are only certain fixed orbits allowed in the atom. An atom will only be excited to a higher orbit, if it ...
Gerard's user avatar
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Why are there spectral lines at all?

My somewhat basic understanding of the concept comes from lectures I've attended about the Bohr-model, which explains the phenomenon as arising from the fact that certain configurations of an atom can ...
Andreas Hagen's user avatar
17 votes
5 answers
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Why is sunlight spectrum continuous?

My teacher explained today that unlike the spectrum obtained by analyzing the sunlight, the spectra of atoms are not continuous. I have a question about this - the sunlight is emitted by the atoms of ...
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How can the discrete atomic spectrum be observed?

My teacher told me that in an atom (assume hydrogen), as soon as the single electron absorbs a photon with the right amount of energy, it jumps up to another energy level, and instantly falls back ...
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What is the difference between the Balmer series of hydrogen and deuterium?

In my quantum mechanics textbook, it claims that the Balmer series between hydrogen and deuterium is different. However, I was under the impression that the Balmer series $$H_\alpha, H_\beta, H_\...
user2654176's user avatar
11 votes
4 answers
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What does ionization of neutral Hydrogen have to do with "transparency"?

Most accounts of the early history of the Universe make some reference to (re)ionization as being the reason that the Universe becomes transparent after a period of opacity caused by the absence of ...
orome's user avatar
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How do electron configuration microstates map to term symbols?

I am trying to understand energy levels of electron configurations. I visited the NIST web site and discovered that the notation used here are called term symbols. After reading corresponding ...
Jamin's user avatar
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Is the Energy of an absorbed photon exactly the energy of the band gap?

I was wondering, if the Energy of a Photon which is absorbed by an Electron, hast to be exactly the Energy of the bound gap. So if i have two energy levels in an atom $E_2$ and $E_1$, does my ...
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Do cosmological and Doppler redshift produce different patterns?

For a given black body radiation curve, would the changes to the spectrum resulting from cosmological expansion and those from Doppler effects be distinguishable on the basis of the shapes of the ...
orome's user avatar
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What is a 'good' coherence/correlation function for multimode spectra?

Following up on the question here and this answer in particular, I would like to pose the following question: How to derive a formula for the coherence length of a multispectral source, such as a ...
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Why do High Pressure Gases produce a Continuous Spectrum?

I am aware that low pressure/density gases produce an emission spectrum as there are specific energy transitions that the electrons can make, emitting certain frequencies of EM waves. However high ...
Nanoputian's user avatar
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Why is a plastic bag transparent in infrared light?

This is a classic trick to do with a IR camera: Bu why is the plastic bag transparent, while the glasses aren't? I've also heard that water is not transparent in IR light. What causes this phenomena?
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What is the probability that a star of a given spectral type will have planets?

There is a lot of new data from the various extrasolar planet projects including NASA's Kepler mission on extra-solar planets. Based on our current data what is the probability that a star of each of ...
dagorym's user avatar
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10 votes
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Explaining deviations in simulated to experimental Cs-137 spectrum

I'm comparing a Geant4 (Monte Carlo based) simulated gamma spectrum of $^{137}$Cs to my experimental results using a NaI(Tl) detector. I find good agreement between the two for the main features such ...
erkoo's user avatar
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2 answers
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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 ...
Marta's user avatar
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2 answers
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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 ...
6 votes
1 answer
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How do we determine what distant planets, stars etc are made of?

I remember this being covered somewhat back in school and I have casually read about it. I know it involves inferring from spectral analysis what physical properties an object may have right? Though ...
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How can we describe the electrons of multi-electron atoms (i.e. not Hydrogen) when equations/analytic solutions only exist for Hydrogen?

I've been digging into emission spectra of different elements and found that such things as the Rydberg equation, Bohr's model, and quantum mechanics can only fully describe the single electron in the ...
Greg's user avatar
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Why is interference there when pulses do not overlap in space and time?

Why is there interference present between the two pulses when looking at the spectrum, if they clearly do not overlap in time, and assumingly in space as well (since $x=ct$)? The spectrum is detected ...
Capo Pavel Mestre's user avatar
5 votes
1 answer
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Natural linewidth of hyperfine transitions

I'm referring to this question: Natural linewidth of hyperfine levels? Let's take Rubidium-85 for example. It's written everywhere that the D2 line has a linewidth of around 6 MHz. But the D2 "line", ...
Philipp's user avatar
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What's the difference between NMR and EPR?

Both NMR and EPR describe the response of magnetic spin to external field. When collecting data, how do you know you're looking at nucleus spin flip or electron spin flip? In other words, since every ...
Sparkler's user avatar
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Black body radiation and spectra lines

My understanding was that all objects emit light of continuous spectrum when hot ( black body radiation) but then you see discreet wavelengths in spectra lines and I am confused. I know I am making a ...
user31058's user avatar
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3 votes
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What determines the form of the intensity curves in Laser-Induced Fluorescence (LIF) measurements?

What determines the form of the intensity spectra of different particle species in Laser-Induced Fluorescence (LIF) measurements? See e.g. I figure that bigger particles have more ways to get ...
Nikolaj-K's user avatar
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2 votes
4 answers
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Why is the Planck function continuous and not discrete? [duplicate]

If we imagine a object made up of Hydrogen gas that is optically thick to all radiation, and is in thermal equilibrium, then, microscopically, photons will be emitted and absorbed as emission/...
quantum_n00b's user avatar
2 votes
3 answers
4k views

Why X-ray and radio waves can penetrate walls but light can not? [duplicate]

Why can visible light, which lies in the middle between X-ray and radio waves in terms of frequency/energy, not penetrate walls?
USER249's user avatar
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Non Adiabatic Coupling Term in Born Oppenheimer Approximation

I am attaching a section from a text book (Conical Intersections Electronic Structure, dynamics and spectroscopy: David R Yarkony & Horst Koppel). Here I am not understanding the so called 'Non ...
albedo's user avatar
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Learning about spectrometers (curvy tungsten spectrum)

I have performed an experiment in which I used a spectrometer (CCS200 from Thorlabs) to measure the spectrum of a tungsten source (it was connected to the spectrometer with an optical fiber). The ...
Vladimir Vargas's user avatar
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2 answers
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What's the difference between microscopy and spectroscopy?

Both methods collect particles or electromagnetic waves, and in both methods it's possible to reconstruct a 2D image, which may represent morphology (AFM, LEED for example), electronic structure (STM, ...
Sparkler's user avatar
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1 answer
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The solar spectrum on the time domain

This is the solar spectrum by wavelength: By formula $c=f\lambda$, we can plot the solar spectrum over the frequency domain: Then we can conduct inverse Fourier transform to transform the plot into ...
LianNuo 's user avatar
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1 answer
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How are we able to observe Fraunhofer lines in a star's spectrum?

How is it possible to observe Fraunhofer lines in the emission spectrum of any star, since the elements absorbing the radiation couldn't possibly absorb all the radiation corresponding to a particular ...
UVcatastrophe's user avatar
-1 votes
1 answer
244 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, ...
Mathematical Curiosity's user avatar
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1 answer
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Does my green laser pointer emit three distinct frequencies, or is my measurement flawed?

I was playing around with a cheap diffraction grating and my set of laser pointers, and I noticed that while the red and the blue pointers produce a single point in the spectrum, my green laser ...
Roman Starkov's user avatar
9 votes
1 answer
722 views

Natural linewidth of hyperfine levels? [duplicate]

The D2 line of $^{87}\mathrm{Rb}$ is the transition between the $5^2\mathrm P_{3/2}$ and the $5^2\mathrm S_{1/2}$ states. Its linewidth $\Gamma$ is always quoted to be $\sim 6\ \mathrm{MHz}$. But both ...
SuperCiocia's user avatar
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7 votes
1 answer
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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 ...
Menschmaschine's user avatar
7 votes
1 answer
3k views

Spectroscopic properties of hydrogen: H vs. H2

One of the basic experiments everybody learns about when it comes to physics is the spectroscopy of hydrogen gas. The typical set-up has a charge discharge lamp containing the hydrogen. The resulting ...
user_na's user avatar
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6 votes
1 answer
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How to convert cm$^{-1}$ to eV?

I know that $1 \:\mathrm{cm}^{-1} = 8065.54429 \:\mathrm{eV}$. I know that wave-number has unit $\:\mathrm{cm}^{-1}$ and that $E=hc\times \mathrm{wavenumber}$. But how do I arrive to the number $...
Filip Landgren's user avatar
6 votes
2 answers
3k views

Polarisation of Light and Atomic Excitation

How does an atomic transition between ground and excited states depend upon the direction of polarisation of incident light?
Rahul's user avatar
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5 votes
1 answer
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Why is the mean free path length of an electron in a solid described by a "universal curve"? (doesn't include electron density)

I've been experimenting with XPS (X-ray photoelectron spectroscopy) and learned that the depth from which the observed electrons originated depends on their mean free path length, which makes sense to ...
Wihtedeka's user avatar
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5 votes
1 answer
949 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 ...
ChemEng's user avatar
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1 answer
688 views

Gravitational Stark Effect

Could gravity induce line splittings in the optical spectrum of a molecule similar to the Stark or Zeeman Effects? Naively, a gravitational potential would be a simple addition to the Hamiltonian ...
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5 votes
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Resolving power of a diffraction grating?

I was working thru a derivation of the resolving power of a diffraction grating at the $n$th order. Here is that derivation: Let us say we have a diffraction grating width $W$ and are looking at ...
Quantum spaghettification's user avatar
4 votes
2 answers
1k views

Do rainbows show spectral lines from water?

A spectral line is the electromagnetic radiation emitted when the electron jumps from higher orbital to a lower orbital of an atom. Water mainly consists of two elements namely hydrogen and oxygen, ...
user6760's user avatar
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4 votes
3 answers
7k views

Why do stars have absorption spectra?

Absorption spectra are a result of light of a certain wavelength exciting an atom from a lower energy level to a higher one and at the same time being absorbed. However, the atom should eventually go ...
Itai Bar-Natan's user avatar
4 votes
2 answers
3k views

Is a detailed absorption spectrum available for carbon dioxide from 300-1100nm?

I believe that carbon dioxide does not absorb light in the visible region, but is a spectrum available somewhere online that shows this as a fact? As in a straight horizontal line at 100% transmission?...
Slarty's user avatar
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3 votes
1 answer
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Can this simple spectrometer be precise without collimation?

Consider the following spectrometer structure: Here the slit can be changed in size, and the lens and detector can be moved closer to or farther from the diffraction grating. I was trying to get ...
Ruslan's user avatar
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3 votes
3 answers
647 views

Why can’t we see atoms in an optical microscope?

I know, the answer to this question may seem obvious: The resolution/magnification of an optical microscope is limited by the minimum wavelength one uses. This is due to the diffraction limit. However,...
Lockhart 's user avatar