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

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Spectroscopy Question

So if we were to view the visible spectrum of a white dwarf star. Would the planetary nebula essentially block what would be an absorption spectrum? If so, would we all just see emission lines. I'm ...
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34 views

Vibrational quantum notation

Reading articles on spectroscopy I often see this notation: 30001 <- 01101, 00011 <- 00001 in context of molecular ...
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122 views

Line-shape asymmetry in undergraduate Hydrogen-Deuterium experiment

I'm working as an LA (undergraduate TA) for an undergraduate physics laboratory experiment where students test the Bohr model and use reduced mass to determine the approximate mass of the neutron. In ...
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1answer
138 views

Thermionic emission, delayed emission and predissociation

In molecular photodissociation, the thermionic emission, delayed emission and predissociation are the same? Otherwise, what is the difference between them? My question is not about the solids, but I ...
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54 views

How large would the electric field need to be to split the mj -/+1 626.6 nm line of neon?

I am an undergraduate considering an extension on a quantum beats experiment with neon. The premise is to excite neon atoms coherently from a metastable 'ground' state into a superposition of excited ...
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2k views

Do excited electrons drop back to same quantum state?

I'm trying to wrap my head around spectroscopy, therefore, I am looking for as complete an answer as possible here, hence why I have broken the question into a different points. Here is what I know ...
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1answer
3k views

What is the correct relationship between light intensity and wavelength?

So we looked at the emission line spectra of noble gases in the lab today (hydrogen, neon, helium). And I noticed that the brightest spectral line in the helium spectrum is the yellow one and the ...
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1answer
46 views

How to begin using SDSS data?

SDSS has gone through so many updates, it's difficult to find out how to access the data today in 2015. How can I use SQL and Python to access SDSS data, e.g. the photometry and spectra of quasars, ...
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151 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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332 views

What is meant by a “sodium line”?

What speed should a galaxy move with respect to us so that the sodium line at $589.0\ \mathrm{nm}$ is observed at $589.6\ \mathrm{nm}$? In the above question what's meant by a sodium line? The ...
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2answers
420 views

Do all elements spectrum lines fall within the visible light range?

I was wondering if whether we were extremely lucky to have found spectral (absorption) lines of astronomical objects because they fell within the visible light range or if there something intrinsic ...
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73 views

What happens to light at sharp points? [closed]

At the tip of the sharp point shown, what will happen to light incident on it. This curiosity was invoked by a friend and also my childhood of watching shiny pointed swords in cartoons. Original ...
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1answer
101 views

Spectral series' formula of a given atom (other than hydrogen-like)?

The hydrogen spectral series is given by the Rydberg formula: The energy differences between levels in the Bohr model, and hence the wavelengths of emitted/absorbed photons, is given by the ...
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1answer
2k views

Ba K Lines in a Cs-137 gamma ray spectrum

I'm looking at a spectrum for the gamma ray spectrum of a 137-Cs source and I'm not sure where the peak in the lower energies of ~32keV comes from. I understand that it's to do with some sort of ...
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1answer
335 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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7k views

Full Width Half Maximum (FWHM) of a transmission spectrum

I have a transmission spectrum of a material which has been fit to a Lorentzian. According to Wikipedia here and here, FWHM is the spectral width which is wavelength interval over which the ...
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732 views

How would you explain spectrum and spectral analysis to grandma?

E.g. what the light or sound spectrum is, what it's useful for - in very simple terms that a grandmother or a child would understand.
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1answer
146 views

How much can a laser's position be fine-tuned?

Suppose you wanted to do a time-resolved experiment with a molecular beam traveling at, say, 300 m/s involving a mobile excitation (pump) laser that scans across the length of the molecular beam and a ...
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1answer
27 views

Should I see evidence of neutron induced gammas on a background spectrum?

If I am looking at a background gamma spectrum taken from a neutron spallation source whilst the beam was off (IE in a shutdown period), should I expect to see emissions coming from neutron induced ...
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2answers
35 views

Gamma spectroscopy - Fitted Singlet

I'm using some gamma acquisition and analysis software. When I ask the software to do some sort of Nuclide Identification, almost every single peak in the generated output is marked with "F". ...
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1answer
53 views

How was hydrogen gas (H) obtained by spectroscopists? Why is there more H than H2 in space?

Introductory quantum mechanics lessons talk about emission and absorption spectra for the hydrogen gas, and then give you an explanation as if this gas were pure $H$ atoms, and not the $H_2$ molecule ...
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2answers
47 views

On energy levels and emission of photons

This is a very basic question but I cannot seem to find the answer anywhere. Say we have an atom in ground state. Its first energy level is 2 eV. An incoming photon of energy 2.5 eV hits an electron ...
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1answer
75 views

Continuous spectra of photons

I guess this is a basic quantum mechanics problem, but I'm not entirely sure of my answer. Suppose we have an electron in a hydrogen atom having the state \begin{equation} ...
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1answer
79 views

Why is solar eclipse so important for sunlight spectrum analysis?

People wait for decades to catch the chance of a solar eclipse to observe the sun. Why cannot they do it every noon?
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90 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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1answer
55 views

Can scientists tell the energy levels of the atom?

In the hydrogen spectral series how did the scientists know the number of the energy level which the electron is moving from or to?
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2answers
3k views

How to calculate the total angular momentum (J) values

How can I calculate the values of $J$ (total angular momentum) for a particular term, for instance, ${}^3P$?
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1answer
157 views

Can I prove boundedness of an operator without checking it for its whole domain?

(I don't have a direct reference so this is a little fishy and I'll delete it if nobody recognises what I'm talking about, but I though for starters I'll ask anyway) I've heard at university that if ...
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26 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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39 views

Why don't stars re-emit the photons they absorb, thus restoring a continuous emission spectrum?

If you shine white light through a gas, electrons can absorb sufficiently energetic photons to reach higher excited states. This produces gaps in the spectrum and it's how Helium was discovered. So ...
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1answer
22 views

Finding natural linewidth's

I want to check whether my fit parameter for the width of a Lorentzian fit on my digital spectroscopy data for Helium (the 5875 Angstrom line) is what you would expect from the uncertainty principle, ...
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1answer
15 views

Could IR and Raman be measured simultaneously?

IR and Raman are measured using two different machines. Looking at the nature of excitation and at the way data is collected, it seems that these two measurements could be done simultaneously (or with ...
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1answer
414 views

Photometric surveys vs. Spectroscopic surveys

I consistently read about certain astronomical surveys which are either described as "photometric surveys" or "redshift surveys". I'm still unclear as to how these two methods differ. Photometry ...
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1answer
58 views

Why is there no fluorescence background in CARS?

In CARS (coherent anti-Stokes Raman scattering), the detected signal is blue-shifted with respect to the excitation - how does this mean that there is no fluorescence or that the fluorescence can be ...
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1answer
286 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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1k 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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49 views

Where can I find spectral data for materials?

The chemical library of ChemSpider has a dedicated section for spectra, but I haven't found any materials that have such data. Is there a (public) database of spectral data?
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3answers
161 views

Can stimulated emitted photons be absorbed?

Typically a stimulated photon will be one of a pair with its stimulating photon. If the leading photon is absorbed by a particle in the ground state, will it then be re-emited by the stimulated ...
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1answer
353 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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1answer
114 views

Resonance Raman spectroscopy vs fluorescence

In Resonance Raman Spectroscopy we often want to avoid the fluorescence. But what is the problem with fluorescence . What we want is a shift between exciting line and emitted radiation and both can ...
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1answer
94 views

Intereference rings by light transmission?

Recently I recorded UV-Vis spectra of liquids with a two-beam spectrometer (Perkin Elmer 900). Lack of proper racks for cells of 0.5 cm optical path length let me use a stack consisting of a 0.2 cm ...
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1answer
63 views

Limits of laser spectroscopy for determining size of a molecule or particle

Say you have a number of particles respectively molecules suspended in air. The diameter of the particles $d_{particle}$ are of the order 1 to 100nm. Can you actually, i.e. in practice, measure the ...
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106 views

Mysterious spectra?

In my blog post Why riemannium? , I introduced the following idea. The infinite potential well in quantum mechanics, the harmonic oscillator and the Kepler (hygrogen-like) problem have energy spectra, ...
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3answers
2k 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
657 views

Calculating Kramers-Kronig using Mathematica [closed]

First of all, I know there is a Mathematica group in beta, but I don't think the problem of the following is directly a Mathematica issue. I am trying to calculate the change of the refractive index ...
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1answer
33 views

Heterodyne detection

According to Phase-stabilized two-dimensional electronic spectroscopy the local oscillator, LO, used for heterodyned signal detection always arrives first at time $t_4$, which is -700fs. In ...
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1answer
91 views

Uncertainty in the average of a series of photon counting measurements

I'm a bit stuck on a problem relating to statistics in photon counting. I'm measuring a spectra with a spectrometer and can set a measurement time and number of times to repeat the measurement in ...
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3answers
217 views

How is this possible that photons are absorbed?

From the lessons on QM, I got impression that there are some discrete orbitals that emit light when electron drops from one to another. Specific molecules emit light in very narrow bands, therefore. ...
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1answer
117 views

photon absorption by atoms causes heat?

I have came up with a weird doubt: photon absorption by atoms causes heat? I mean, I was always told that if the photon's frequency is the magic one, the atoms absorbs the photon and goes to an ...
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1answer
64 views

Switching a PMT from PC-mode to DC-mode: What happens?

I was wondering a bit how it is possible to switch a photo multiplier tube from the photon counting mode to the DC (I assume direct current)-mode. If I simply add a high voltage (as usual), I get the ...