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

learn more… | top users | synonyms

3
votes
1answer
534 views

Wigner Threshold law in Photodetachment and Photoionization

I am writing this question here because I have a problem in understanding the Wigner Threshold law in Photodetachment and Photoionization. The Wigner Threshold Law is given by: $\sigma$=$E^{L+1/2}$. ...
12
votes
1answer
5k views

How do we know the temperature on the planets?

I was watching a show and they were saying that the temperature of Pluto (I know it is not a planet) is about $-300 {}^\circ F$. I know that depends where in the orbit Pluto is, but how do we ...
2
votes
0answers
62 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 ...
0
votes
1answer
24 views

Equivalent electrons, terms of atomic subshell

Let's say I consider $p^2$ case. For non-equivalent electrons it gives six possible terms: $\{^1S, ^1P, ^1D, ^3S, ^3P, ^3D\}$. When we consider equivalent electrons, Pauli principle, obviously ...
1
vote
1answer
282 views

Why is an exciton only observed when we excite to the conduction band and not to other electronic level inside the bandgap?

Excitons can be observed when we excite electrons to the conduction band. I don't know about excitons being observed when we excite the electrons to an electronic level that would eventually be in ...
0
votes
0answers
14 views

Is spectroscopic analysis of flowing air sensitive to the amount of matter or the flux?

I would like to like to go deeper in understanding the analytical and physical behaviour of air quality analysers. AQ analysers are merely based on spectroscopy (absorbance, fluorescence, ...
0
votes
2answers
28 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 ...
1
vote
1answer
208 views

On characteristic X-ray spectra and relative intensity

I am looking at the following image (from http://www.schoolphysics.co.uk/age16-19/Atomic%20physics/X%20rays/text/X_ray_spectra/index.html): and I want to know, of the two curves, which one ...
0
votes
0answers
19 views

How do the optical properties of glass influence the efficiency of solar thermal flat plate collectors

A solar thermal flat plate collector (FPC) converts irradiation into heat. The usfull energy gain of such a FPC can be expressed as: $$ Q_u = F_R \cdot A \left[ I\tau \alpha - U_L \cdot \left(T_i - ...
1
vote
1answer
43 views

What is the spectrum of a nuclear bomb in a vacuum?

This question about 'nukes in space' mentions that the two forms of energy released from a nuclear bomb come from neutrons and photons (the latter about 104 times the former). It's mentioned that the ...
6
votes
1answer
111 views

Symmetries of atomic orbitals, s-state forms a triplet!

I have a trouble understanding how s-subshell electrons can form a triplet state ever. In general isn't it true, that there are only two cases for s-state: $\ell=0$, $s=1/2$, $J=1/2$ - doublet (one ...
0
votes
1answer
19 views

A good book on spectroscopy

I have found out that there are two kinds of books on spectroscopy: chemistry prospective experimental physics prospective I am looking for a book which contains more or less rigorous theoretical ...
0
votes
1answer
144 views

Nuclear explosion wavelength data

I am looking for data source (or chart) of spectral data that is being emitted on detonation of nuclear or thermonuclear explosion. Reason I am looking is to see if this data has specific signature ...
1
vote
2answers
54 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?
2
votes
1answer
83 views

Why infrared absorption is a nonlinear technique?

I am looking for a good explanation explaining why infrared absorption technique is essentially nonlinear (eg. for carbon monoxide quantification). When using UV/visible/near-IR absorption technique, ...
5
votes
2answers
239 views

Self-study: resources for understanding Gamma spectroscopy

I work in applied mathematics and have no background in atomic physics. I need to have a good understanding of the principle and application of Gamma spectroscopy. I am ok to spend the needed time but ...
4
votes
1answer
536 views

Calibrating the relative intensity of a spectrometer with a blackbody source?

I am trying to compare the relative brightness of $H \beta $ and $H\alpha$ lines using a CCD spectrometer. In order to correct for the different grating efficiency at the two different wavelengths. I ...
2
votes
4answers
258 views

How do we demonstrate that all spectral colors exist in nature?

Spectral emission by elements occurs in discrete wavelengths. There are only about 118 elements. My question is whether there are pure colors either disfavored in nature, or even disallowed? The sun ...
0
votes
0answers
9 views

Why is gas phase UV vis spectra broad?

I read about an experiment, in which gas-phase UV Vis spectra is given. It is broad. I don't understand why? Because broadening happens in liquid state due to Franck Condon effect, but not in gas ...
6
votes
3answers
91 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 ...
4
votes
4answers
4k views

Why in professional spectroscopes diffraction gratings are used instead of prisms?

Why in professional spectroscopes diffraction gratings are used instead of prisms? I guess transparency is not an issue, as we need optics anyway.
2
votes
1answer
140 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 ...
11
votes
1answer
428 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 ...
2
votes
0answers
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 $\hbar \omega _2$ ...
1
vote
2answers
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 ...
0
votes
0answers
26 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$) = 44.316 GHz B($...
0
votes
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 $e''$ ...
3
votes
1answer
42 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 ...
0
votes
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 ...
1
vote
1answer
50 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 ...
0
votes
0answers
7 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 ...
0
votes
2answers
71 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 ...
2
votes
2answers
150 views

What will be the effect of placing a light source very close to a photodiode?

What will be the effect of placing a photodiode really close to a laser source and what should be the appropriate distance between a light source and photodiode to get maximum output current?
3
votes
2answers
39 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 ...
1
vote
1answer
35 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 2D-...
1
vote
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 ...
1
vote
0answers
72 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 ...
0
votes
2answers
999 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}).$...
2
votes
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 ...
2
votes
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 ...
0
votes
0answers
11 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?
0
votes
0answers
10 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?
6
votes
4answers
13k 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 ...
0
votes
0answers
32 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 ...
0
votes
0answers
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 ...
1
vote
1answer
38 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 $\...
1
vote
1answer
28 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 ...
-1
votes
3answers
57 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 ...
0
votes
0answers
21 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 ...
3
votes
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 ...