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# Questions tagged [spectroscopy]

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

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### What are the proper steps for taking a reflectance / tranmission spectrum of a solid sample?

When I began taking spectra of samples, I was lucky to have a spectrometer that basically did everything for me and produced spectra of samples that I would expect from literature. I am now using an &...
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### Calculating Bandgap of material from specular reflectance vs diffuse reflectance

I am looking for some clarification on whether specular reflection data can be used to calculate the bandgap of a material. I am using a UV-vis spectrometer and measuring the reflectance from an ...
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### Is precessional frequency of hydrogen nucleus in H-NMR equal to angular frequency of magnetic component EM radiation?

I asked the same question on chemistry stack exchange but got no answer over there. So, I'm posting it here in the hopes that I'll find some sort of answer:) Suppose we have a hydrogen nucleus. Now, ...
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### X-ray absorption edge, accurate theoretical predition possible?

It is well known that in X-ray absorption spectroscopy, the absorption spectrum shows discontinuities at some critical frequencies. Is it possible to predict locations of these jumps theoretically? I ...
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### Does this double well potential contradict the fact that there is no degeneracy for one-dimensional bound states?

This example is taken from Modern Quantum Mechanics by Sakurai. Consider a symmetric double well potential in one-dimension with a barrier of height $V_0$ and width $a$ at the middle. The eigenstates ...
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### What is emission line ratio?

As the header stated, what exactly is the 'emission line ratio'? Like, [O III]/Hβ or [Ne V]/[Ne II]. Recently I've been reading some research papers in astronomy and astrophysics pertaining to ...
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### Zeeman splitting of a spectral line in the presence of a strong magnetic field as compared to that of a magnetic field of intermediate strength

Will the number of spectral lines into which a spectral line will split due to an electronic transition from a P state with spin=1/2 to a S state with spin=1/2 be more in the presence of a strong ...
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### What happens after a Photon pass-es through an element without causing any ElectronTransition? e.g. A Cube of Scanadium [closed]

Assuming:- No ElectronTransition ==> Photon passes through the atom. [right?] Longer Version In Words:- If a Photon doesn't have enough energy / has more energy than to trigger a ...
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### When an element near the star surface absorbs the discrete frequency of star's em radiation do this absorbed photons ought to accumulate?

We all know about emittion lines that are empty from a discrete em freqency depending on the element that absorbs that frequency band near the star which we observe when looking at these astrophysical ...
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### Total blackbody spectrum from two objects at different temperatures

I was wondering what the intensity spectrum would look like when collecting the light emitted by two objects (same material properties, emissivity etc.) at two different temperatures. Or alternatively,...
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### At what point does a line spectrum become a continuous one?

I have 1 main and 1 sub question, please dont remove my post for this i just want to clear this up its been bugging me, thanks. Fundamentally, I don't understand 2 things, and if anyone could clear ...
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### Why does photoelectric effect not affect the absorption spectrum?

What I know Photoelectric effect When the surface of a metal is irradiated with an electromagnetic radiation of frequency more than the threshold frequency of the metal, then the photon of the ...
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### How to create a spectral image from a gas?

Let's say I want to put air through an optical spectrometer. It doesn't need to be NASA accurate, but suppose I just want a rudimentary measure of carbon from the carbon frequencies. How can I get &...
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In chapter 14 of Jackson the number of photons per unit frequency interval is given by: How can I go from $\frac{photons}{d \omega}$ to a flux expressed in photons per second per 0.1% bandwith $\frac{... • 51 0 votes 0 answers 20 views ### What physical processes are involved in causing the Voigt profile in X-ray diffraction I understand qualitatively that a Voigt profile combines both Gaussian and Lorentzian profiles which is a suitable method for plotting an X-ray diffraction pattern. Which physical processes lead to ... 1 vote 1 answer 28 views ### What is the emission spectrum of an igniting match? I took this photo of a burning match just after striking. There are clear emission lines rippling throughout the spectrum and a huge peak in the orange. Nowhere online could I find a lit match ... • 131 0 votes 0 answers 37 views ### What happens after bulk gold absorbs a photon with its energy at the band gap or higher (wavelength < 500 nm)? As is explained in the answers of this question: Why are most metals gray/silver? nicely, the responsible transition occurs between the 5d orbital and the 6s orbital, which is relativistically shrunk ... • 121 0 votes 0 answers 50 views ### Synchrotron radiation calculation details and expressing the flux In chapter 14 of Jackson the energy radiated per unit frequency interval per unit solid angle is given: Integration over the angles gives: Finally, dividing by$\hbar \omega$equation (14.91) gives ... • 51 2 votes 0 answers 53 views ### Is the electromagnetic wave emitted during an atomic electron transition always sinusoidal, and why is there a spectral linewidth? I recently engaged in a discussion regarding Planck's relation, which posits that the energy$E$of a photon is directly proportional to its frequency$f$, symbolized as$E=hf$. The user @Sturrum on a ... 0 votes 0 answers 27 views ### Spontaneous transfer (decay) between Zeeman states In a paramagnetic substance like Rubidium (due to its unpaired valence electron), under the influence of a DC magnetic field, the degenerate electronic energy states split into Zeeman states. Let's ... • 342 1 vote 1 answer 89 views ### The relativity of simultaneity in two-photon absorption In the two-photon absorption (TPA) process, when there is no intermediate state, it's required that two photons are absorbed either simultaneously or semi-simultaneously, with a relatively short time ... • 342 5 votes 1 answer 236 views ### Koopman's Theorem for Ionization energy and electron affinity Why is Koopman's theorem a reliable approximation for ionization energy but unreliable for electron affinity? I understand that it has to do with cancellation of errors by orbital relaxation and ... 1 vote 1 answer 92 views ### Doubt in a method to determine the spectral terms for equivalent electrons E. R. Tuttle in 1967 proposed a suitable method to determine the spectral terms for equivalent electrons in an atom in LS coupling condition. You may download the paper here, or E. R. Tuttle; Terms ... 0 votes 0 answers 52 views ### Difference between the spectrum of hydrogen and black body radiation [duplicate] So I'm learning about blackbody radiation and radiation in general. As I understand it, there are 3 ways to transfer energy/heat: convection, conduction and radiation. In chemistry I also learnt about ... 2 votes 1 answer 81 views ### Rotational quantum states for atoms It is well-established that molecules possess rotational and vibrational quantum states, due to molecular symmetries, in addition to electronic states. In contrast, it is generally accepted that atoms ... • 342 1 vote 1 answer 26 views ### Spectroscopy on colored flames When observing colored fire through a spectrometer after adding substances like copper chloride or magnesium sulfate to change its color, what specific spectra are typically observed? How does the ... 1 vote 2 answers 53 views ### The relative phase of photons in two-photon absorption In two-photon absorption (TPA), the relative polarization of the two photons about to be absorbed simultaneously by an atom is crucial in determining the TPA rate. However, there is a lack of ... • 342 1 vote 0 answers 22 views ### Understanding and researching with Spectroscopy I am very new to physics so don't know a whole lot yet, so please correct any incorrect vocabulary you may find. Papers that are easy for beginners to understand are also very welcome! Context: I am ... 0 votes 0 answers 41 views ### Head-on collision of$\rm N_2$and$\rm CO_2$molecules [duplicate] Consider a standing sound wave formed in the air in conditions close to standard pressure and temperature in the antinode region. On the molecular level, it will involve multiple collisions of air ... 1 vote 1 answer 29 views ### What is the meaning of dynamically generated states in particle physics? In hadron spectroscopy, a structure may be interpreted as various "configurations", such as conventional quark-antiquark states, tetraquarks, hybrid states, dynamically generated states or ... 0 votes 1 answer 39 views ### What determines the wavelength in absorption? When looking at absorption or reflectance spectra, say in the range of 400nm to 2500nm, you can see peaks (or dips) at certain wavelengths, that are characteristic for the material absorbing and ... • 111 0 votes 1 answer 58 views ### Why is red the brightest in the emission spectra of Hydrogen Gas? I was studying a very simplified intro to Spectroscopy. The following diagram shows the emission spectra of Hydrogen Gas: Credit: NASA, ESA, and L. Hustak (STScI) My Question: In the spectra, the ... • 1,066 2 votes 3 answers 116 views ### Why does the rotational level spacing increase when moment of inertia decrease? In the rigid rotor approach we obtain the result that the spacing between different rotational energy levels in a particular vibrational state is$\nu = 2B(J+1)$and$ B = \frac{ h }{ 8 \pi^2 Ic }$, ... 0 votes 0 answers 50 views ### Ground state bleach in transient absorption with at least 3 states The ground state (GS) bleach (B) is usually described by "less absorption due to depletion of electrons in the ground state". See here. But the bleaching should also occur when there are ... • 535 6 votes 1 answer 114 views ### How do we know that the Sun is 71% Hydrogen by mass from emission/absorption spectra? In my Intro to Astronomy ("intro" is very important, please keep responses as simple as possible) course, we're currently learning about light and electron orbitals and such, and I came ... 4 votes 1 answer 145 views ### About the focal length and$f\#$of spectrometers Suppose I image light into the entrance slit of a spectrometer (actually a monochromator). The spectrometer is schematically shown below. On the spectrometer's specs sheet, it is said that it has a ... • 117 1 vote 1 answer 142 views ### Why is a voigt model have a more physical meaning than a gaussian when looking at lineshape in spectrscopy? I was discussing this with my professor, he was saying that the Voigt model has a physical meaning in terms of actually being reproducible in physical terms when curve fitting to spectral lines. ... 1 vote 0 answers 40 views ### Can Raman spectrometers detect Rayleigh scattering? Can Raman spectrometets detect Rayleigh scattering? The sample I have got turned blue after annealing. And I am wondering if this happened because of Rayleigh scattering. I saw some articles about ... 0 votes 0 answers 38 views ### How to convert$\rm W/m2/sr/nm$to$\rm kR/nm$[duplicate] How do I convert spectral radiance$\rm W/m2/sr/nm$to$\rm kR/nm$? I tried the following method from this paper: https://opg.optica.org/ao/abstract.cfm?URI=ao-13-9-2160 • 11 2 votes 1 answer 139 views ### Nature of absorption spectra peaks similar profile in Dimethyl sulfide (C$_2$H$_6$S) I was reading interesting article about possible life signs detection in exoplanets, where JWS telescope have captured that exoplanet K2-18 b atmosphere has Dimethyl sulfide traces. This chemical ... 1 vote 0 answers 83 views ### Converting$\rm W/m2/sr/nm$to$\rm kR/nm\$ for any wavelength

I have atmospheric spectra given in W/m2/sr/nm units and wavelength in nm. I want to convert W/m2/sr/nm to kilo Rayleigh/nm (kR/nm) for any wavelength. I tried the following method from this paper: ...
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### Extremely strong peak around 10 eV energy of Aluminum crystal in an x-ray inelastic scattering experiment

I conducted an experiment where I measured Bragg reflection for two different atomic planes (200 and 400) of Aluminum crystal at an energy of 10 KeV. Then, in each of these two measurements I shifted ...
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### Advantage of a single large telescope over many small ones for optical/infrared spectroscopy?

In a thought experiment where we would like to do optical/infrared spectroscopy on distant galaxies, and in which we would like to increase as much as possible the resolution of the spectroscopy (...
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### Can I use the Ph. Eur. definition for signal-to-noise to determine limit of detection for spectroscopic data?

The European Pharmacopoeia defines the signal-to-noise ratio (S/N) as follows: S/N = 2H/h Where H is the height of the peak from the baseline and h is the range of the background noise. Now on to my ...
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### Getting the spectrum of light source at high intensity (for low transmittance measurement)

I am trying to measure the transmittance spectrum through a liquid sample using a visible-NIR spectroscopy (a spectrometer connected to a fiber optics and a collimating lens at the end), with tungsten-...
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### Is the Fourier Transform a reliable way to infer the physical phenomena producing an RF signal?

Consider the following thought experiments: Scenario 1: A person standing far away shines 3 light beams at you, each beam having a narrow spectral distribution centered around different frequencies F1,...
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