the practice of separating a signal by frequency (or sometimes energy or momentum) and analyzing the resulting spectrum.
17
votes
2answers
346 views
Experimental observation of matter/antimatter in the universe
Ordinary matter and antimatter have the same physical properties when it comes to, for example, spectroscopy. Hydrogen and antihydrogen atoms produce the same spectroscopy when excited, and adsorb the ...
13
votes
3answers
134 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 ...
9
votes
2answers
2k views
Why is a plastic bag transparent in infrared light?
This is a classic trick to do with a IR camera:
Bu why is the plastic bag transparent, while the glasses aren't? I've also heard that water is not transparent in IR light. What causes this ...
8
votes
3answers
185 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 ...
7
votes
1answer
226 views
Emission line width units
What do these units mean: the large velocity widths of emission lines (in AGN) are 2,000 - 10,000 km s^-1? I've looked for the answer but keep getting swamped in myriads of details. I want to know ...
7
votes
1answer
143 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 ...
6
votes
3answers
852 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?
6
votes
2answers
698 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 ...
5
votes
1answer
994 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 ...
5
votes
1answer
590 views
How do we determine what distant planets, stars etc are made of?
I remember this being covered somewhat back in school and I have casually read about it. I know it involves inferring from spectral analysis what physical properties an object may have right?
Though ...
5
votes
2answers
1k views
Relation between total orbital angular momentum and symmetry of the wavefunction
My question essentially revolves around multi-electron atoms and spectroscopic terms. I understand the idea that the total wavefunction for Fermions should be antisymmetric. Consider as an example, ...
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 ...
4
votes
2answers
81 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 ...
4
votes
1answer
103 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, ...
4
votes
4answers
357 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
4answers
130 views
Is it possible to see Fraunhofer lines with amateur equipment?
Is it possible to see Fraunhofer lines with amateur equipment?
Would it be possible (with reasonable effort) to identify elements or is this hard?
4
votes
2answers
165 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 ...
4
votes
2answers
145 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 ...
4
votes
1answer
578 views
Selection Rules in electron spectroscopy
How to derive the selection rules $\Delta L= \pm 1$, $\Delta S=0$ for electron spectroscopy?
4
votes
1answer
117 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? ...
4
votes
1answer
42 views
Do XAFS excitations and subsequent relaxations lead to vibrationally hot molecules?
I'm in the process of trying to understand X-Ray Absorption Fine Structure (XAFS) spectroscopy, but I think this question is more fundamental than merely as it pertains to XAFS. I think I don't ...
4
votes
1answer
287 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 ...
3
votes
3answers
166 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 ...
3
votes
3answers
963 views
Why do stars have absorption spectra?
Absorption spectra are a result of light of a certain wavelength exciting an atom from a lower energy level to a higher one and at the same time being absorbed. However, the atom should eventually go ...
3
votes
1answer
368 views
Phonons, rotons, and maxons
What are phonons, rotons, and maxons, and what does their dispersion curve have to do with superfluidity? I understand that they are quasiparticles, but I'm not entirely sure what that implies. Are ...
3
votes
1answer
161 views
Is it possible to determine timescales of electron dynamics from the natural linewidth of an electronic transition?
A lot of work has been done recently on electron dynamics using attosecond pump-probe techniques; for instance in this paper. In this particular paper, the authors photoionized the neutral ...
3
votes
1answer
246 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 ...
3
votes
3answers
85 views
Atmospheric interference and ground based stellar observations
Stellar spectra captured from ground based equipment needs corrections to remove atmospheric spectral noise. Is there an Internet site that shows specific amplitude and wavelength differences between ...
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 ...
3
votes
1answer
70 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 ...
3
votes
1answer
187 views
How small of a depletion signal can the best modern mass spectrometers detect?
So I know the answer to this question varies widely across mass spec techniques, masses, and, of course, budgets, but my question is about the best case scenario for all of these variables (although ...
2
votes
2answers
191 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. ...
2
votes
1answer
209 views
Suns emission spectrum
I learnt that in astrophysical spectroscopy, the emission spectrum of distant stars is used to determine what they're made of. So why is it that our own Sun is emitting the whole spectrum ? (or is ...
2
votes
2answers
281 views
Do cosmological and Doppler redshift produce different patterns?
For a given black body radiation curve, would the changes to the spectrum resulting from cosmological expansion and those from Doppler effects be distinguishable on the basis of the shapes of the ...
2
votes
3answers
908 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 ...
2
votes
2answers
734 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
115 views
THT (Tetrahydrothiophene) absorption spectrum
I am looking for the absorption spectrum of THT. What is the best way to find these types of exotic material's spectral characteristics?
2
votes
3answers
1k views
Why do we take the first derivative of EPR/ESR spectra?
Apologies if this question is a bit too chemistry-flavoured.
In electron paramagnetic resonance spectroscopy, there's a practically ubiquitous convention of plotting the first derivative of the ...
2
votes
3answers
583 views
Unstable energy levels
Well, reading about "Raman Effect" I saw that when the electron absorb some energy, with frequency $ \omega_{abs} $, that is different from $ \omega_{n} - \omega_{n-1} \neq \omega_{abs1} $, it go to ...
2
votes
3answers
600 views
Photon absorption probability for a given molecule in gas phase
So I'm pretty sure I'm approaching this problem in the wrong way and I need some guidance (my first hint is that I think I'm thinking about a quantum mechanical problem too classically)
Suppose there ...
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
71 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 ...
2
votes
1answer
62 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 ...
2
votes
2answers
298 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 ...
2
votes
1answer
317 views
How can I subtract Spectra?
I am writing an application that should allow to view and manipulate spectra (Raman).
I am only given one normal spectrum consisting of 1024 coordinate points. Plus I have a background spectrum that ...
2
votes
2answers
356 views
Absorption Spectral Broadening
I'm working on a research project involving absorption spectra of particulates in solution. I was curious if someone could clarify or direct me to a resource that explains broadening mechanisms ...
2
votes
2answers
1k views
How do electron configuration microstates map to term symbols?
I am trying to understand energy levels of electron configurations. I visited the NIST web site and discovered that the notation used here are called term symbols.
After reading corresponding ...
2
votes
3answers
354 views
Light emission spectrum units
Do someone knows the units of the spectra provided here ? It seems obvious enough that it's said nowhere, but even Wikipedia and other sites are quite blurry on this point.
So, is it power ($W$), ...
2
votes
2answers
75 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 ...
