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

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Detecting molecules in space?

http://www.forbes.com/sites/alexknapp/2012/02/24/nasa-detects-solid-buckyballs-in-space/ I refer to the above article, which mentions that buckyballs "far smaller than the width of a hair" were ...
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28 views

Converting spectra to rgb colour

I am having trouble obtaining RGB colour values from the spectra of an object. I have the specific flux $F_\nu$ as a function of $\nu$ for each pixel of the image I'd like to make, but am unsure of ...
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35 views

What causes this IR emission in UV 365nm LED?

I've just got access to spectrometer and measuring spectrum of everything. But when I took a look at 365nm UV led from chinese UV flashlight I got something really strange - it had some IR at exactly ...
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18 views

Can near-infrared spectroscopy distinguish between various metals?

Can near-infrared spectroscopy be used to distinguish metals from another? If not, why not?
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127 views

How is this possible that photons are absorbed?

From the lessons on QM, I got impression that there are some discrete orbitals that emit light when electron drops from one to another. Specific molecules emit light in very narrow bands, therefore. ...
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30 views

How was hydrogen gas (H) obtained by spectroscopists? Why is there more H than H2 in space?

Introductory quantum mechanics lessons talk about emission and absorption spectra for the hydrogen gas, and then give you an explanation as if this gas were pure $H$ atoms, and not the $H_2$ molecule ...
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29 views

Difference between Rayleigh scattering and fluorescence spectroscopy [closed]

How can we differentiate Rayleigh scattering from fluorescence spectrum?
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72 views

Is the Energy of an absorbed photon exactly the energy of the band gap?

I was wondering, if the Energy of a Photon which is absorbed by an Electron, hast to be exactly the Energy of the bound gap. So if i have two energy levels in an atom $E_2$ and $E_1$, does my ...
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24 views

Estimation of source irradiance given the spectral sensitivity of the instrument and spectrum of the source

I am trying to measure the irradiance of a UV source, but the available instrument has a different sensitivity. Suppose the black line corresponds to the spectral sensitivity of the instrument ...
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31 views

Is it possible to calculate the relative abundances of elements in the sun based on its line spectrum using a common lab spectroscope?

There are many problems that I feel would hinder the process: atmospheric noise, light pollution etc. Let's assume that I bypass these problems and get an accurate emission line spectrum on the ...
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30 views

What does 'easily reversed' mean in the NIST spectral database? [closed]

Cross posted to http://engineering.stackexchange.com/q/3303/ I'm trying to do some processing of optical emission spectra from sputtering plasmas, and am confused by what NIST means by 'easily ...
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22 views

Deconvoluting Raman spectras from different wavelengths

I am using a laser source that is wider than typical laser source for Raman spectroscopy. This mean that the full width at half maximum (FWHM) of the laser is about 5-10 nm, compared to the normal 1-3 ...
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51 views

Spectroscopy from a classical light wave or photon only?

In chemistry we mostly regard light/electromagnetic radiation as a beam of particles or photons. This is a very useful model to explain molecular excitations and ionisations from quantum interactions. ...
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84 views

Having trouble understanding spectral lines

In my notes I wrote that Rutherford's model of the atom could not explain spectral lines, because that is what my textbook says. I'm not really sure about the details of spectral lines though. I know ...
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11 views

Hyperfine structure interval rule only obeyed approximately?

The hyperfine interaction is given by $\Delta E = A \langle I \cdot J \rangle = \frac{A}{2}\left[ F(F+1) - I(I+1) - J(J+1) \right]$. The interval rule is given by: $$ \frac{\Delta E_{F,F-1}}{\Delta ...
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28 views

Asymmetric photoluminescence spectra

Why do photoluminescence spectra have asymmetric lineshapes as those here http://www.scielo.br/img/revistas/bjp/v37n4/a04fig01.gif or here: ...
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27 views

On energy levels and emission of photons

This is a very basic question but I cannot seem to find the answer anywhere. Say we have an atom in ground state. Its first energy level is 2 eV. An incoming photon of energy 2.5 eV hits an electron ...
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16 views

Does water absorb microwaves above of beneath its relaxation frequency

I am a bit confused about the concept of relaxation frequency. In my course text we derived a model with the help of Newton's law to describe the movement of polar molecules in an electromagnetic ...
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27 views

PM-IRRAS Equidistant Fringes in Spectrum

What is the cause, and best method to prevent / minimize, fringes in one's FTIR (PM-IRRAS) spectrum on samples deposited on a thin metal film? The fringes look as though they are spaced out by a ...
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22 views

Sonoluminescence spectrum

During cavitation created by sound in a liquid the collapse of the bubbles can lead to very high temperatures and pressures resulting in the emission of light - sonoluminescence. Can the spectrum of ...
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9 views

Velocity Selective Coherent Population Trapping and recoil limit on temperature

I have read that it is possible to go under recoil temperature limit using VSCPT (Velocity Selective Coherent Population Trapping) and that this method is based on atoms trapping in quantum state in ...
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41 views

photon absorption by atoms causes heat?

I have came up with a weird doubt: photon absorption by atoms causes heat? I mean, I was always told that if the photon's frequency is the magic one, the atoms absorbs the photon and goes to an ...
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17 views

Doppler and recoil limit on temperature

I havent't understood the causes of Doppler limit and recoil limit. I have found on the net different observations about them ("Doppler limit is due to the fact that the atom can't have a smaller ...
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46 views

Can anybody explain about phase shift and phase spectrum terms in case of multidimensional signal?

I know about phase of a 1D signal, but when I move into higher dimensions like 2D or 3D etc, it becomes headache to grasp the concept. What do the terms "phase shift" and "phase spectrum" mean in ...
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23 views

Why graphene's substrate is important

I just have some feelings that somehow it is important what specific subtrate is used to grow graphene monolayer on. Some substrates are better, another ones are not so good. But I cannot completely ...
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33 views

Optical spectrometer

I am new on optical spectrometer, my particular interest is the spectrometer in which the deflection is produced by diffraction in a diffraction grating. But I can not find a good schematic and the ...
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58 views

How to measure temperature of a laser cooled sample at picoKelvin temperatures?

I'm reading about laser cooling.. my question is: how can the temperature of the sample be measured? (using laser cooling we can reach $10^{-12}K...)$
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45 views

How to deal with coma and oblique spherical aberration in a Czerny Turner configuration?

I am modelling my own spectrometer using Zemax when all of a sudden I've been told that: even if you manage to optimize the angles or positions of the grating and the mirrors, you won't get ...
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115 views

What are the purposes of slits inside a spectrometer (Czerny-Turner)?

I am building a Raman spectrometer with a Czerny Turner configuration (with RamanPi). Why does the light source (A) appear to be converging into the entrance slit (B)? When a sample is excited by ...
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1answer
27 views

How to convert the molar attenuation coefficient, ie. molar absorptivity, to heat capacity?

In spectroscopy techniques, such as infrared spectroscopy, light of a certain wavelength is absorbed. I see parallels to the concept of heat capacity, i.e. the heat necessary to change the temperature ...
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20 views

Reflectance spectrum and Real Refractive Index Relation

I have taken in the laboratory mesurment of the Reflectance spectrum of a material and via mathematica calculated the phase for Kramers-Kronig Relations,and finnaly i calculated from it the real part ...
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1answer
12 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 ...
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40 views

What is the reason that EXAFS are done with monochromatic x-ray light?

Why is the light incident on the samples in EXAFS experiments monochromatic? What would happen if a broad bandwidth hits a grating and then all the diffraction spectrum goes through the sample and is ...
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Does the EXAFS oscillations occur when ultrashort x-ray pulse is used? Electron with a 50eV kinetic energy will travel in 0.1fs 4.2 Angstroms

In X-ray extended absorption spectroscopy (EXAF) an electron is excited by an x-ray photon into the continuum, the outgoing electron wave interferes with the scattered electron wave from the ...
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56 views

Angle-resolved photoemission spectral (ARPES) function from band Hamiltonian

I am trying to derive spectral function for a band Hamiltonian. I am using http://arxiv.org/abs/cond-mat/0306084 as a prototype reference. I do not understand how the coherence factors $u_k$ and $v_k$ ...
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57 views

Why does the refractive index not mirror the Lorentzian peak shape of the absorption index?

In the characterization of materials, there are many methods used: One of them is infrared spectroscopy. In a lab we saw the indices of refraction and absorption of a certain (semiconductor) solid ...
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47 views

Rotational Spectrum of a Diatomic Molecule

The rotational energy levels of a diatomic molecule are given by $$E_l=\frac{\hbar^2}{2I}l(l+1)$$ where $l$ is an integer. If the molecule is a dipole it can emit or absorb electromagnetic radiation ...
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257 views

Does my green laser pointer emit three distinct frequencies, or is my measurement flawed?

I was playing around with a cheap diffraction grating and my set of laser pointers, and I noticed that while the red and the blue pointers produce a single point in the spectrum, my green laser ...
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1k views

Why do lines in atomic spectra have thickness? (Bohr's Model)

Consider the atomic spectrum (absorption) of hydrogen. The Bohr's model postulates that there are only certain fixed orbits allowed in the atom. An atom will only be excited to a higher orbit, if ...
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32 views

Why does the spectrum for deuterium show a weak line at H-alpha?

I was wondering why the spectrum for deuterium shows a weak line at H-alpha, the first line in the hydrogen spectrum.
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142 views

What's the difference between NMR and EPR?

Both NMR and EPR describe the response of magnetic spin to external field. When collecting data, how do you know you're looking at nucleus spin flip or electron spin flip? In other words, since every ...
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304 views

Resolving power of a diffraction grating?

I was working thru a derivation of the resolving power of a diffraction grating at the $n$th order. Here is that derivation: Let us say we have a diffraction grating width $W$ and are looking at ...
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92 views

Photometric surveys vs. Spectroscopic surveys

I consistently read about certain astronomical surveys which are either described as "photometric surveys" or "redshift surveys". I'm still unclear as to how these two methods differ. Photometry ...
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1answer
40 views

Why is there no fluorescence background in CARS?

In CARS (coherent anti-Stokes Raman scattering), the detected signal is blue-shifted with respect to the excitation - how does this mean that there is no fluorescence or that the fluorescence can be ...
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73 views

Resonant vs. Non-resonant Raman

What does it mean to say that the conventional Raman effect is non-resonant? And, how/why does resonant Raman give a stronger signal than the non-resonant type?
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495 views

Sun spectroscopy - Home experiment

We let the sun light run through a 5x3x3cm triangular glass prism and we examined the formed 'rainbow' in search of Fraunhofer lines. However, even though we looked close enough (even with a ...
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117 views

What is meant by a “sodium line”?

What speed should a galaxy move with respect to us so that the sodium line at $589.0\ \mathrm{nm}$ is observed at $589.6\ \mathrm{nm}$? In the above question what's meant by a sodium line? The ...
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1answer
22 views

Spectroscopy - Absorption lines

Let's say we run a light source (a strong torch) with full spectrum light through a big, transparent, glass box filled with neon. Will we be able to see any Fraunhofer lines on the spectral analysis ...
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47 views

Bandwidth-Pulse Duration Relationship

Assuming Gaussian pulse, the relationship between pulse duration and bandwidth is given by: $$\Delta \nu \cdot \tau \geq 0.441$$ If the rms bandwidth and rms pulse duration are used, then the ...
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85 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, ...