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

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1answer
925 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 ...
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1answer
158 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
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1answer
228 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 ...
2
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1answer
126 views

How do micro-channel plates detect neutral molecules?

Micro-channel plate (MCP) detectors are used to detect photons, electrons or charged particles. But how can MCPs be used to detect neutral particles? In ion traps, the neutral molecules (after being ...
3
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2answers
158 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 ...
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1answer
54 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 ...
4
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1answer
209 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? ...
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1answer
96 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, ...
4
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1answer
298 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, ...
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1answer
89 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 ...
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3answers
1k 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 ...
3
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1answer
127 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 ...
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1answer
102 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 ...
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1answer
99 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
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1answer
185 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 ...
2
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0answers
48 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 ...
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1answer
542 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 ...
7
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1answer
259 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 ...
3
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1answer
233 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 ...
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3answers
156 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 ...
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1answer
91 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 ...
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0answers
83 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
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2answers
196 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 ...
3
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1answer
87 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 ...
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3answers
5k 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 ...
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1answer
183 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
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2answers
112 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 ...
3
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2answers
1k 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 ...
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2answers
280 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 ...
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3answers
262 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 ...
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1answer
216 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
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1answer
416 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 ...
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1answer
226 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.
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3answers
459 views

How would you explain spectrum and spectral analysis to grandma?

E.g. what the light or sound spectrum is, what it's useful for - in very simple terms that a grandmother or a child would understand.
2
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1answer
636 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 ...
7
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1answer
525 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 ...
2
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2answers
343 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
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1answer
523 views

Calculating Kramers-Kronig using Mathematica

First of all, I know there is a Mathematica group in beta, but I don't think the problem of the following is directly a Mathematica issue. I am trying to calculate the change of the refractive index ...
2
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2answers
2k 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
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1answer
179 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
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1answer
254 views

Confusion concerning the use of wavenumber in exercise about Fabry-Perot etalon

In the exercise we are given that the spectrum of a light source consists of two spectral lines, which both have wavelengths around $500 \text{ nm}$ and the separation between them - given in ...
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4answers
189 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 ...
7
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1answer
2k 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 ...
6
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1answer
2k 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 ...
3
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1answer
255 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 ...
7
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4answers
609 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
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2answers
101 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 ...
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2answers
154 views

Relationship of the abundance of an isotope and the vapor pressure

Say I have a sample of some alkali metal - Rubidium for example. A sample of Rubidium consists of approximately 27% $^{87}$Rb and 73% $^{85}$Rb. Does the vapor pressure of each isotope individual ...
5
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1answer
409 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 ...
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0answers
125 views

Linewidth pressure broadening due to organic molecules

In relation to atmospheric spectroscopy and some other gaseous spectroscopy applications where organic molecules are present in the vapor, does anyone know of any papers or resources on pressure ...