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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2answers
809 views

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 ...
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28k views

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 ...
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784 views

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 ...
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Why is spectrum obtained by sunlight, said to be continuous?

My teacher spoke about atomic spectra today, and he explained that, unlike the spectrum obtained by analyzing the sunlight, the spectra of atoms are not continuous. I have a question about this - ...
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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 ...
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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 ...
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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_\...
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647 views

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 ...
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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 ...
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1answer
100 views

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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2answers
599 views

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 ...
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1answer
327 views

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 ...
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2answers
4k views

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 ...
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9k views

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, ...
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127 views

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 ...
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1answer
5k views

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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2answers
4k views

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 ...
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3answers
476 views

Why is the planck function continuous and not discrete?

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/...
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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 ...
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2answers
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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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1answer
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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 ...
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1answer
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Blackbody radiation and Spectral Lines [duplicate]

Blackbody radiation is thermal radiation from a hot object emitted over a continuous range of wavelengths. But why are spectral lines, lines (i.e., you only get certain wavelengths when an element is ...
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1answer
855 views

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 ...
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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?
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240 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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How to define the light “color” from a given spectral distribution?

The following question may be naive and incomplete in some way I don't know. I'm not a specialist on spectroscopy, colours and light curves, color spaces, etc. Suppose you have a simple power-law ...
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2answers
941 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, ...
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1answer
5k views

Bleaching groundstate

I'm reading an article about two-dimensional infrared spectroscopy and I don't understand the following sentence. Bleach or stimulated emission contributions yield negative signals. What are "...
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1answer
169 views

Relative weights in rotational bands of symmetric diatomic molecules

In an old paper, Ehrenfest 1931, the introduction starts off as follows: The band spectra of symmetric diatomic molecules show certain striking differences from those of asymmetric molecules. For ...
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1answer
924 views

Temperature dependence of spectra

I have a question that is short and sweet: Are spectra (both fluorescence and absorbance) of any molecule dependent on temperature? In particular, is the spectral lineshape function of any molecule ...
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1answer
1k views

Where to find detailed measured emission spectra of all chemical elements?

I'd like to have something like this, but for single atoms and with more extended range of wavelengths. All I could find e.g. for hydrogen was lots of talks about Rydberg formula etc. and plots of ...
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3answers
5k views

Franck Condon Principle and Born Oppenheimer approximation

My question here is purely fundamental. I am confused with the concept in Franck Condon (FC) principle and Born Oppenheimer (BO) approximation. The FC principle is in accordance with the BO ...
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1answer
982 views

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 ...
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3answers
3k views

What is decay associated spectra?

What is decay associated spectra? Suppose we measure the fluorescence intensity over different wavelengths and over time, we get: $$I(\lambda,t) = \sum_i^n \alpha_i(\lambda) \exp(\frac{-t}{\tau_i}).$...
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1answer
1k views

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 ...
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1answer
453 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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5k 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 ...
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1answer
1k views

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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2answers
1k views

Why are overtones forbidden within the harmonic approximation?

In vibrational spectroscopy only transitions between neighboring vibrational states ($\Delta \nu = \pm 1$, $\nu$ being the vibrational quantum number) are allowed within the harmonic approximation. ...
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1answer
683 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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4answers
1k views

Machine to identify substances

I was looking at Wikipedia's article on mass spectrometers, and realized that the method described was to heat a sample into its gas phase and separate the ions by mass using a large magnet. While I ...
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3answers
1k views

Unstable energy levels

Well, reading about "Raman Effect" I saw that when the electron absorb some energy, with frequency $ \omega_{abs} $, that is different from $ \omega_{n} - \omega_{n-1} \neq \omega_{abs1} $, it go to ...
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2answers
164 views

Doppler spectroscopy to verify Earth's speed around the sun

I'm looking for data points to check changes in $z$ as the Earth moves towards and away from a star. I'm finding lots of data for various objects [1] but lots of variation too (for eg, the results for ...
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2answers
260 views

How is hydrogen able to emit a light spectrum with only one electron?

When light is shined through hydrogen gas, three colors of light appear. The issue I have with this is that hydrogen has one electron, meaning somehow the electron has to be emitting all three of ...
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Is there a mathematical model that models spectral power distribution curves?

The experiment was aimed to find the specturm cruve of different light bulbs experimentally. Is there a mathematical way to justify the results I obtained (the plotted graph)? Would the equation in ...
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0answers
132 views

What's the difference between “spectromicroscopy” and “microspectroscopy”? [duplicate]

Both definitions that I found are rather vague. (Related question: What's the difference between microscopy and spectroscopy?)
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35 views

What combination of stable GE isotopes make up the germanium in a Ge(Li) spectrometer

I work with a Ge(Li) gamma spectrometer. I'm trying to work out the different populations of stable Germanium isotopes in it. I'm trying to model the unrealistic scenario where none of these isotopes ...
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1answer
1k views

Resonant vs. Non-resonant Raman

What does it mean to say that the conventional Raman effect is non-resonant? And, how/why does resonant Raman give a stronger signal than the non-resonant type?
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What does this notation mean: $\mathrm{O}_{2} \ \ a\,{}^{1} Δ_{g} ← X\,{}^{3}Σ^{-}_{g} $?

The notation (which I found in the abstract of this paper) is $$\mathrm{O}_{2} \ \ a\,{}^{1} Δ_{g} ← X\,{}^{3}Σ^{-}_{g}. $$ Any help with this? I understand it's talking about quantum states of ...
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3answers
2k views

Having trouble understanding spectral lines

In my notes I wrote that Rutherford's model of the atom could not explain spectral lines, because that is what my textbook says. I'm not really sure about the details of spectral lines though. I know ...