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

learn more… | top users | synonyms

1
vote
1answer
249 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
1answer
26 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 ...
2
votes
0answers
54 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} ...
1
vote
0answers
15 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 ...
1
vote
1answer
862 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, ...
2
votes
1answer
411 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: $\sigma$=$E^{L+1/2}$. ...
10
votes
1answer
4k 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 degrees. I know that depends where in the orbit Pluto is, but how do we determine ...
0
votes
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 ...
0
votes
0answers
27 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 ...
2
votes
2answers
123 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?
2
votes
0answers
23 views

What is the origin of the naming convention for the various branches in vibration-rotational spectroscopy?

In vibration-rotational spectroscopy, the different spectral lines are grouped into branches for different changes in the total angular momentum, i.e. $$ \begin{array}{rrrrrr} & \mathrm{O} & ...
1
vote
0answers
25 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 ...
0
votes
0answers
10 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 ...
2
votes
1answer
200 views

Total magnetic moment in an atom

I have a doubt regarding the calculation of total angular momentum of electron in an atom. Which is the right way to do it? Method 1: Total magnetic moment $$ \begin{align} \vec{\mu_J} &= ...
1
vote
1answer
125 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 ...
0
votes
1answer
21 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 ...
6
votes
3answers
582 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 ...
1
vote
4answers
2k views

Spectrometer vs. Spectrophotometer

I have been researching about the difference of a spectrometer and a spectrophotometer. They both sound the same. What is the difference?
0
votes
0answers
15 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 ...
0
votes
1answer
28 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.
0
votes
0answers
26 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 ...
0
votes
0answers
63 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 ...
0
votes
0answers
32 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 ...
3
votes
0answers
28 views

Book on spectroscopy (line dependency on parameters)

I am trying to find a book (undergraduate level) on Spectroscopy. I am interested in how molecular absorption lines depend on parameters like temperature and pressure (for example with gases). Can ...
2
votes
1answer
178 views

Which g factor in an EPR spectra is the right one?

I was reading this introduction to EPR and it seems to imply both that there is a unique g-factor of a given compound, but also that we can calculate multiple g-factors for a compound. For example, ...
0
votes
0answers
34 views

Difference between three mutually complementary methods: Raman, Infra-red spectroscopy and inelastic incoherent neutron spectroscopy?

When I read the wiki on Raman spectroscopy, I found a paragraph explaining what system is suitable for using Raman and what others do not. It provide two other method as shown in title: infrared ...
0
votes
1answer
23 views

Why higher FAT level implies more signal in XPS analysis?

In XPS analysis, the FAT (Fixed Analyzer Transmission) parameter controls the electrostatic field of an emispheric analyzer, called Pass Energy $E_P$. The FWHM of a peak of signal is given by ...
0
votes
0answers
14 views

Gamma spectroscopy - Extractable information from peak significance changes?

Apologies for the title - I couldn't think of a better way to summarize my question I have a table which contains information on 60 gamma spectra taken over a total period of 20 days, from the hall ...
1
vote
1answer
249 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 ...
1
vote
0answers
43 views

Quantum beats and Quantum mechanical side of photosynthesis

I have two questions. One concerning quantum beats alone, another - process of photosynthesis. I am very well aware that there is strong evidence suggesting that mechanism that leads light through, ...
1
vote
0answers
27 views

Can one measure experimentally the average distance between the two electrons in the excited state of helium in the singlet versus triplet states?

$\frac{1}{\lvert\ \vec(r_{1})-\vec(r_{2})\rvert}$ is a hermitian operator so I am supposing there could potentially be an observable with this which might be experimentally measured. We can measure ...
0
votes
0answers
44 views

Beta decay - Relative probability of electronic conversion for different disexcitations energies

I'm studying, experimentally, beta decay phenomena. Internal conversion of electrons happens when we have a sobreposition between a excited nucleus with it's electronic cloud. The colision between the ...
2
votes
1answer
37 views

Antisymmetry requirement for the total wavefunction

My understanding is that if we are dealing with a system of two electrons, the total wavefunction needs to be antisymmetric only when the two electrons have same value of n and l ( i.e. they are ...
0
votes
0answers
22 views

How can I determine if a peak in a spectrofluorometer's spectrum is erroneous?

Let me give you the specific scenario since I'm really not sure which factors are relevant or not: Our lab made our own upconversion nanoparticles (UCNP) following a popular paper on the subject. ...
0
votes
0answers
19 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 ...
2
votes
1answer
31 views

How deep within the sample can the DOS(density of states) be detected by STM(scanning tunnel microscope)?

Using STM equipment, we can get the LDOS(local density of states) on the surface of a sample. I want to know whether the LDOS within the sample(not surface) can be detected by STM. what is the ...
3
votes
2answers
70 views

Why is the blue line in the Balmer series sometimes not visible?

So I've conducted an experiment to find the four visible hydrogen emission spectrum lines in the Balmer series in a laboratory. I don't have any background in quantum physics. When I looked through ...
15
votes
4answers
3k views

Why can't I see the blue color scattered by the lower atmosphere of the earth?

I understand that the blue colour of the sky is because of the scattering of blue light by molecules in earth's atmosphere. The scattering appears to be happening from molecules that are far above in ...
0
votes
1answer
35 views

FWHM increase with energy (gamma spectra)

Below I have two plots from a gamma spectrum which I've been analyzing. The first plot is between a low energy range, the second between a significantly higher energy range. It is clear that the FWHMs ...
1
vote
1answer
10 views

Sound range and depth it travells whe it hits sound

I know most people hear from 20hz to 20000hz and about the absorption spectrum of water absorption spectrum of water link but how deep does sound travel when it hits the skin and which range of ...
2
votes
0answers
49 views

In what cases would using a non-resonant spectroscopy be preferable to using the resonant type?

Here it is mentioned that non-resonant Raman spectroscopy is desirable for avoiding fluorescence and for studying water due to water's low polarizability. How is non-resonant Raman desirable in the ...
2
votes
1answer
48 views

Dispersion in ultrafast lasers

In mode-locked Ti:sapphire lasers, positive dispersion is caused mainly by the crystal. A prism pair placed in the laser resonator can compensate for some of the dispersion by introducing negative ...
1
vote
2answers
27 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". ...
0
votes
2answers
35 views

What happens to the velocity map image if the plane of polarization is not on the plane of the detector?

In an electron Velocity Map Imaging (in Velocity Map Imaging in general) it is required that the plane of polarization to be parallel to the plane of the detector (in other words, plane or ...
4
votes
1answer
43 views

How do space probes identify molecules?

How does a space probe identify molecules without actually obtaining the molecules? The common identification techniques I can think of are spectroscopy and magnetic resonance, but for both of them, ...
0
votes
0answers
27 views

determination of electron dispersion curves

I am somewhat new to quantum physics and I am studying electron dispersion band structures of SiC like the one here I want to know what spectroscopic techniques/methods or if they are spectroscopic ...
3
votes
1answer
975 views

What is the secondary electron cutoff in ultraviolet photoelectron spectroscopy?

While the fasted emitted electrons comes from the fermi level of the material in UPS measurement, where does the slowest, which is called secondary electron cut-off orginate from? I really can't ...
5
votes
7answers
909 views

Why is absorption spectrum a line spectrum?

The minimum energy required to excite a hydrogen electron is 10.2 eV. When photons of energy spread over a continuous range of wavelengths fall on a sample of hydrogen, why are only those photons ...
0
votes
1answer
13 views

Is it possible to do IR spectrometry with emitter and photoresistor on the same side?

When doing spectrophotometry, there is generally a light source that emits the light that then passes trough whatever you want to measure, and then on the other side, a photoresistor that can sense ...
0
votes
1answer
33 views

How does this type of pump-probe spectroscopy work?

In optical Kerr effect spectroscopy, a pump beam causes a temporary birefringence in a sample, while a probe beam measures the return of the sample to equilibrium. Here’s a schematic: The pump and ...