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

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Doppler-free saturation spectrscopy line

Throught he Doppler-free saturation spectroscopy technique I can see the absorption lines of $^{39}$ K: The hyperfine structure of the excited state (D2 line) of K is not resolved enough to see the ...
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1answer
425 views

Why is the spectrum of old stellar populations characterized by broad lines?

I'm taking a course in astrophysics and my teacher said that old stellar populations have broad lines whereas young populations have narrow emission lines. My first thought was to consider then case ...
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30 views

Distribution of quantum beating among spectral frequencies

Let's imagine that we have 3-level system: ground state $\vert 0 \rangle$ and two excited states $\vert 1 \rangle$, $\vert 2 \rangle$ with similar energies $\hbar \omega _1$ and $\hbar \omega _2$ ...
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24 views

Determining bond length of HCN using rotational constant (Physical Chemistry 2)

Context: 2nd year undergraduate student taking Physical Chemistry II. Question: Determine the HC and CN bond lengths in HCN from the rotational constants: B($^{1}H$$^{12}C$$^{14}N$) = 44.316 GHz B($...
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1answer
27 views

Does the sign of imaginary part of complex permittivity have any physical meaning?

I have noticed some papers having written complex permittivity as $e' + je'' $ and others as $e' - je''$. The data in literature does not specify the sign. What should I use and does the sign of $e''$ ...
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1answer
40 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 ...
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1answer
25 views

Absorption spectra of molecules library

Do you know where I can find a library with absorption spectra? I would like it if then I could input a wavelength and get back a specific value. More specifically I would like to see the absorption ...
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5 views

Can I approximate the emission line FWHM for an etalon through doppler broadening?

I'm asked to find the finesse for an etalon needed to make the Zeeman effect of the red Cd line measurable. I found the Zeeman separation of the lines to be about $7 GHz$ for the apparatus given. I ...
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2answers
24 views

Gamma spectroscopy - Nuclide identification

I have a question about what the usual practice is for nuclide identification in gamma spectroscopy. For example, if I see a line at 477 keV, I would write that the origin of this line is $^7Be$. As ...
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2answers
33 views

Different width of spectral lines for different groups of stars

As seen in an HR-diagram, a certain stellar classification can correspond to more than one group/sequence of stars (G5 could for instance be either a giant, main sequence star or a white dwarf and so ...
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66 views

Why does fluorescence emission detector pick up second order wavelengths with first order scan, even though they have different angles?

my question in more detail and with an example: Let's say I have a 980nm laser and I use that laser to excite my fluorescent solution in cuvette. My scan range is from 300 to 800nm. If, for example I ...
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1answer
47 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
25 views

Why Doppler shift is applicable to spectral lines alone?

In astronomical spectroscopy, Doppler shift is an important parameter. But why is it applicable to spectral lines alone, and not to the continuous spectrum in the background? Shouldn't the motion of ...
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0answers
39 views

Plasmon quenching vs plasmon decay. What is the difference?

I'm reading an article "Quenching, Plasmonic, and Radiative Decays in Nanogap Emitting Devices" (pubs.acs.org/journal/apchd5). I don't understand the following: Counterintuitively, we evidence ...
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9 views

Lorentzian nature of reflected microwave power in Electron Spin Resonance

Reflected microwave power has Lorentzian shape when plotted against frequency in ESR. How to mathematically prove this?
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10 views

Change in Q factor on tuning external magnetic field in Electron spin resonance experiment

Does the Q factor of the cavity resonator show a dip at the resonant value of the external magnetic field while performing an ESR experiment?If so, what is the physical reason behind it?
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31 views

Which Hydrogen Emission Lines Appear First?

When a blackbody is heated, it radiates photons. At low temperatures, there isn't much radiation at high-energy end of the spectrum but as the temperature raises, high-energy radiation becomes ...
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16 views

What photomultiplier failure causes a zero signal?

I have a photomultiplier detector that suddenly stopped working. Usually I would have expected damage to occur over time by overexcitation, leaving a distorted signal. Now I'm unsure whether the PMT ...
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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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50 views

Calculating Natural Broadening of Emission Lines

I'm trying to demonstrate the small effect of Natural Broadening as compared to other types of broadening (Doppler, Stark, van der Waals, etc.) and my calculations don't match the accepted values. My ...
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20 views

How to calculate term symbols and quantum numbers in spectroscopic physics?

I am studying for an exam in Quantum and Atomic Physics, and I having trouble working out what all of the possible term symbols are for a given electron configuration. So for instance, if I have the ...
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1answer
28 views

Why is a notch filter required for Raman Spectroscopy?

It is my understanding that Raman Spectroscopy uses a notch filter (or sometimes an edge filter) to remove the light from the laser, so only the relevant Raman bands are present. However, if this is ...
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3answers
56 views

What physical properties can't be predicted based on index of refraction? [closed]

If I tell you the real and imaginary parts of the index of refraction for all frequencies, name a property that can't be predicted based on that information. If you're assuming this is a gas, specify ...
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1answer
41 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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27 views

Role of Cavity Resonators in continuous wavelength-electron paramagnetic resonance(CW-EPR)

Why is it necessary to place the sample in a cavity resonator for obtaining EPR spectrum in CW-EPR? What role does a cavity resonator play in a CW-EPR spectrometer?
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17 views

Absorption cross-section in atoms

How could someone calculate the absorption cross-section for an atomic species, not only on a specific atomic resonance, but derive a result, for the dependence of the absorption cross-section from ...
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2answers
49 views

Characteristic frequency

Can you please give me shortest possible (bare basic definition) of the characteristic frequency of a spectrum? All that google gives me are books and articles where I don't understand a word.
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41 views

How come hydrogen produce spectrum in visible light

I am confused, how can hydrogen produce emission lines in the visible light region? the only excitation that can happen to hydrogen is from energy level 1 to any other energy level, all of that ...
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1answer
63 views

Why is intensity related to number of photons?

I have been reading up on Doppler broadening and have found a number of sources (for example here and here) which seem to be taking the number of photons in the range $[\nu,\nu+d\nu]$ to be the same ...
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2answers
68 views

How can only one valence electron in sodium cause doublet in spectrum?

The valence electron in sodium atom gets excited and moves to higher orbital say $3P$ and it then comes to the lower energy state $3S$ thus there should be only one line in spectrum (regarding this ...
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1answer
22 views

Formation of Line Spectra in light of Bohr's Theory [closed]

I am reading about the electronic structure. It is written that when hydrogen's electron comes back to ground state from excited state, it releases energy in a specific amount according to Bohr. But ...
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1answer
23 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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31 views

Spectroscopy: The trustworthiness of reflected, refracted, and “mixed” light sources

Spectroscopy: If spectral lines are used to determine the composition of an object, wouldn’t the reflected light (e.g., from a star) that allows us to see non-luminous objects (e.g., planets, bolides) ...
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3answers
84 views

Why absorption spectum is not identical to emission spectrum?

Hydrogen emission and absorption spectral lines are typically depicted as the same: (source) However, in more complex systems, the emission and absorption spectra are significantly different. For ...
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2answers
68 views

Can we determine the surface temperature of stars other than the sun by using the black body radiation theory?

It is well known that the surface temperature of the sun can be determined by fitting the solar spectrum to the black body radiation spectrum. Is this scheme feasible for other stars? Possibly the ...
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1answer
77 views

Calculate how many photons hitting a sample that are absorbed

In the determination of the quantum yield of a photoisomerization, $\Phi,$ the following is needed $$ \Phi = \frac{\mbox{Number of "reactions"}}{\mbox{Number of absorbed photons}} $$ The photon flux ...
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22 views

How to calculate the magnetic field due to orbital angular momentum in the fine structure

How to calculate effective magnetic field due to the angular momentum L in an atom like Na(23)? I found an answer that we could imagine the case that the atom was orbiting the electron now and ...
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70 views

Estimating temperature with Boltzmann relation with split emission lines

I'm trying to estimate the temperature of a plasma through the use of hydrogen lines, $H_{\alpha}$ and $H_{\beta}$ using the Boltzmann relation: $$ \frac{ n_{2} }{ n_{1} } = \frac{ g_{2} }{ g_{1} }e^...
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1answer
9 views

The $^1S_0 \rightarrow ^3P_0$ transition in O III

Checking out NIST data, I cannot seem to find any data about a $p^2$ valence atom, such as O III, for the $^1S_0 \rightarrow ^3P_0$ transition. Obviously it isn't a electric or magnetic dipole allowed ...
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35 views

Selection rules in a finite quantum well

I have a finite quantum well made of two different semiconductors with different bandgaps and I want to calculate the different transitions between the energy levels possible that I calculated in that ...
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30 views

Variable speed of light impact on spectral absorption lines in distance luminous objects?

There are many other arguments as to the constancy of the speed of light (or more precisely, c). One thing I have been curious is what would the impact be on spectral measurements from distant ...
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12 views

Spectral Signature

I am interested in studying about spectral signature of various materials. I am working as an electronics engineer intern in a company which deals with Hyperspectral imaging. Working with spectral ...
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1answer
18 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
23 views

What is the meaning of the magnitudes on the axes of this spectrum?

I'm taking a course on radiation physics and I've been given an spectrum by my professor (concretely it is a spectrum of $\left.^{22} Na \right.$). This is the first time that I come across this kind ...
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1answer
37 views

Stark broadening and Voigt fitting

I have LIBS spectral data acquired with a CT spectrometer of resolution 0.4nm. I fitted the Voigt profile into the spectral peak at $\lambda_0$. The lorentz $\Delta \lambda_L$ and the gaussian $\...
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1answer
31 views

Where can I find the Auger emission spectra of the most common chemical elements?

I am looking for an online resource where I can find the Auger emission spectra of (most common) chemical elements, i need them for AES (Auger Emission Spectroscopy). Thank you.
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3answers
597 views

How can light emit three kinds of spectra?

In case of black-body radiation, radiation gives continuous spectra. Molecular spectra is an example of band spectra. Similarly, there's also the atomic spectra. Why are the spectra of light not same ...
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1answer
179 views

Exact meaning of “pi/2 pulse”

In studying Mach-Zehnder and Ramsey interferometers, I came across the expression "$\pi/2$ pulse". What does it mean exactly? I am working with a Bloch vector representation $(u,v,w)$ of a 2 state ...
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43 views

Sum rule in X-ray Photoelectron Spectroscopy (XPS)

What is the sum rule in X-ray Photoelectron Spectroscopy (XPS)? how can I derive it? Can anybody explain the principle of sum rule in XPS or in spectroscopy in general? How can I apply it to a ...
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40 views

Multi-photon excitation probability for a two-level system

If a two-level system with a lifetime $\tau$ is excited with a pulse of duration $t_{pulse}$, what is the probability of exciting more than one photon? For simplicity we can take it to be a $\alpha \...