the practice of separating a signal by frequency (or sometimes energy or momentum) and analyzing the resulting spectrum.
6
votes
2answers
721 views
Converting between brilliance, intensity, and flux
This one should be a bit of a softball, but I can't find it explicitly stated anywhere on the internet, and my basic unit analysis doesn't seem to work.
Suppose you have a beam of synchrotron ...
4
votes
1answer
294 views
Why can free lithium atoms not take part in an Auger process?
Shouldn't it be possible for an incoming photon to excite one of the 1s electrons to a 2p state (or one of even higher energy) and then for the excited electron to drop back to 1s and kick out the 2s ...
0
votes
0answers
27 views
Photometric versus radiometric and spectral quantities
Are spectral quantities the same as photometric quantities?
How do you pass from a radiometric quantity $R$ to the correspondent spectral quantity $R_λ$
I've been ask to pass from Irradiance to ...
1
vote
0answers
48 views
How to absorb a characteristic line in a spectrum
I have an x-ray tube. When I see the spectrum, I notice the characteristic lines of the anode. What do I have to do if I want to absorb a characteristic line?
I have thought that I can add a filter. ...
2
votes
1answer
95 views
Can one compute the vibrational spectrum of a bond by the Fourier transform of the dipole moment vector autocorrelation function $C_{\mu\mu}(t)$?
Is it true that one can calculate the vibrational spectrum of a bond by the Fourier transform of the dipole moment vector autocorrelation function $C_{\mu \mu}(t)$?
For example, suppose that I have ...
1
vote
3answers
552 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 ...
0
votes
1answer
52 views
Rutherford Scattering Spectra
I am using SimNRA to simulate the classical Rutherford Scattering. Playing around with it, I came across some spectra that I cannot explain...
First of all, if someone plots the spectrum of ...
0
votes
2answers
56 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
1answer
36 views
Micro channel plate detectors to detect neutral particles
Micro channel plate (MCP) detectors are used to detect photons, electrons or charged particles. But, how MCPs can be used to detect neutral particles? In ion traps, the neutral molecules (after ...
2
votes
3answers
123 views
Can a multipass x-ray absorption cell be constructed?
I've been trying to understand the various concepts behind x-ray optics compared to standard visible/IR optics like mirrors and such. However, the x-ray mirrors I've been finding typically have ...
2
votes
1answer
93 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 ...
4
votes
1answer
124 views
QM with complex eigenvalues
What class of theories/physical systems own finite/infinite complex eigenvalues? I do know that e.g., quasinormal modes of BH do have complex eigenvalues, but are they finite or infinite in number? ...
0
votes
1answer
42 views
UV-VIS spectrometer on Solids
I ran an experiment using translucent single crystal solids. I modified the solids along the way using different chemical/temperature environments. After every stage, I ran the samples through a ...
3
votes
1answer
73 views
Rotational velocity of face-on spiral galaxies using spectroscopy
I am doing my first steps in spectroscopy (IFS actually) and how we can learn more about galaxies by using it. I came up with a simple question which, unfortunately, I can not answer:
How can we ...
1
vote
1answer
31 views
Electronic, vibrational and rotational autoionization
Can anyone please explain me the concept of electronic, vibrational and rotational autoionization.
What I understood is, autoionization usually occurs when the ion core is rotationally or ...
1
vote
1answer
85 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, ...
5
votes
1answer
2k views
Newton's color Disk
How does Newton's color disk work?
Newton's disk - Take a circular white color disk, make 7 equal intersections and paint section with respective VIBGYOR colors, now when you spin the disk in certain ...
0
votes
0answers
32 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 ...
4
votes
1answer
121 views
Very large absorption lines in stellar spectrum
I was puzzled by the wide absorption lines in a stellar spectrum I found. The following is what I expect absorption lines to look like - thin, crisp lines:
However, I found this stellar spectrum, ...
2
votes
1answer
67 views
Absorption cross section for direct dissociation and predissociation - Photoelectric absorption
Why the absorption cross section in direct dissociation process is wide and structureless while the absorption cross section in the predissociation process is structured and containing lines which are ...
1
vote
1answer
59 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 ...
1
vote
1answer
68 views
Dividing two star spectra
I am doing some work that involves dividing two stellar spectra from the same star. Those stellar spectra are constructed by summing random samples of multiple spectra from the same star to improve ...
0
votes
1answer
66 views
Thermionic emission and delayed emission
I want to understand the concepts behind the thermionic emission. In thermionic emission, the energy randomization occurs and the energy may be split to electronic or roto-vibrational states. If this ...
4
votes
4answers
374 views
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 ...
4
votes
2answers
82 views
Metal Dilemma: Only very few civilizations per galaxy
This is a question in the area of extraterrestrial life. While life may be possible without it, space travel is probably impossible without metal. Metal is created in stars and heavy metals (above ...
2
votes
0answers
39 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 ...
8
votes
3answers
200 views
Significance of letters in Hertzsprung-Russell (H-R) diagram
The Hertzsprung-Russell diagram that categorizes star types uses the letter codes O, B, A, F, G, K, and M to indicate a star's temperature/color. Hottest (blue) is O and coolest (red) is M.
What do ...
-4
votes
1answer
130 views
Spectral radiance unit conversion [closed]
I have spectral radiance data in SRUs (spectral radiance units), as a function of wavelength:
$$a = \mu W cm^{-2} sr^{-1} nm^{-1} $$
However, I am working with software which requires my data in the ...
13
votes
3answers
142 views
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 ...
3
votes
1answer
72 views
Does the spectrum of Sol's emission change as it ages?
A follow-up to my earlier question How would one navigate interstellar space? that just occurred to me; albeit on a different tack.
Sol is probably in a state of continuous flux. The change of state ...
4
votes
2answers
175 views
Resources and requirements for amateur spectroscopy
If I wanted to move beyond just looking through my eyepieces and taking photographs of astronomical objects, what can I do do move into astronomical spectroscopy?
Are there any good resources for ...
7
votes
1answer
148 views
Strange light polarization effect?
I spent a while working with MgF2-windowed xenon flash / discharge lamps. Primarily, I characterized their spectra with two normal-incidence spectrometers against a calibrated Deuterium lamp. In this ...
6
votes
3answers
2k views
What is a spectrometer, and why are they so useful in science?
I've heard reference to many telescope and spacecraft that have a device known as a spectrometer, and I'm curious, what is the purpose of these device? What's the working principal behind them and ...
1
vote
3answers
108 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 ...
0
votes
1answer
64 views
Does every wavenumber of IR result in a different kind of vibration?
Does every wavenumber of IR result in a different kind of vibration?
If that is true, what if a molecule absorb 2 different wavenumbers (which cause different rocking and symmetrical stretching for ...
1
vote
0answers
45 views
Correlation function in relaxation in NMR
I am new in this community, I am from a chemistry background. I want to know a detailed solution of a density matrix for a singlet state using the concept of spin lattice relaxation in NMR. I will ...
4
votes
2answers
146 views
Why is 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 phenomena as arising from the fact that certain configurations of an atom can ...
2
votes
3answers
1k 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
1answer
52 views
What is the reference spectrum?
What is the reference spectrum? I need to know how to calculate the reference spectrum of a wavelength 500nm.
2
votes
2answers
78 views
Driving a solution of optical isomer molecules with the resonant frequency
What happens when we drive a solution of optical isomer molecules (enantiomers) with a microwave radiation in resonance with the tunneling frequency of the molecules (the frequency of the transition ...
1
vote
2answers
156 views
How the spectrum of the hydrogen atom is checked/detected experimentally?
When solving the hydrogen atom, as a 2 body problem, we have the motion of the center of mass and the motion relative to the center of mass. The well known energy spectrum, $E_n$, that goes like ...
0
votes
0answers
135 views
Instrumentation how-to: Raman Spectroscopy on single molecules (TERS)
The last two decades have brought a tremendous progress in the high resolution visualisation of single molecules. The molecules reside on an atomically flat surface and the imaging technique used is ...
2
votes
2answers
314 views
Energy shift between hydrogen and deuterium
Stated: The atomic spectra of hydrogen and deuterium are similar however shifted in energies.
So im trying to explain why it is that the emission lines are shifted and how they are shifted.
Since ...
3
votes
3answers
175 views
How do NASA's Curiosity determine the elemental composition of Mars using spectrometer?
From this article on hindustantimes.com - Curiosity sends data about Martian surface:
The resultant flash of glowing plasma is viewed by the system’s 4.3-inch aperture telescope, which sends the ...
-1
votes
1answer
121 views
What is electron momentum density in solids and molecules?
Can someone kindly help me to know how can i get electron momentum density for one orbital like home?
what is the theory of electron momentum density? how can I derive electron momentum density from ...
3
votes
1answer
262 views
Enhance a home build spectrometer
I would like to build a home made spectrometer like it's describing here:
http://coolcosmos.ipac.caltech.edu/cosmic_games/spectra/makeGrating.htm
How can I improve this spectrometer? A prism from an ...
2
votes
2answers
194 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. ...
0
votes
1answer
135 views
Spectroscopic notation $s$, $p$, $d$, $f$, $\ldots$
$s$ is sharp, $p$ for principal, $d$ for diffuse, $f$ for fundamental.
Where do all those term come from? I do not see any link with the corresponding shapes.
3
votes
2answers
2k views
Glycerol: refractive index & absorption spectra in 0.2-0.4um range
Could anyone suggest where can I find absorption spectra & refractive index of Glycerol?
I am specifically interested in UV range, 200-400nm, everything I was able to find out was for standard ...
6
votes
3answers
883 views
Is there a light source that emits all wavelengths of visible light at the same time?
Many light sources like LEDs and lasers only emit a single wavelength of light.
Is there a light source that emits all wavelengths of visible light at the same time?
