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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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Photo Multiplier Tube (PMT) and charge sensitive pre-amplifier

I have an H7195 assembly type Photo Multiplier Tube (PMT) used to be tested for single photon measurement. I would like to use the dynode output to check the spectrum by connecting to a charge ...
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Why hydrogen lines are less visible in the Sun spectrum than in supernovae clouds?

Supernovae clouds are very colorful, and if I trust documentaries I watched, the colors are due to excitation of elements, as in fireworks. Since the Sun is mostly made of hydrogen, I suppose those ...
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What powdered material can be regarded as an ideal Near UV reflector?

I'm looking for some common powder material (like alumina) that's nearly 100% reflective in UV region, to make a compacted power target to use as a reference for 100% reflectance. Or, at least, some ...
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Is it possible to detect the amount of CO2 in the atmosphere by observing Northern Lights?

From my limited understanding, the different colours observed from the Northern Lights is due to the presence of different gases in the atmosphere. Is it possible to observe the amount of CO2 in the ...
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What is 'Spectral Domain'?

In a paper which deals with optical coherence tomography they say they are dealing in the spectral domain. What exactly does that mean?
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Saha-Boltzmann Equation

I am following Ahmed, Ahmed, Rafiqe & Baig A comparative study of Cu–Ni Alloy using LIBS, LA-TOF, EDX, and XRF paper on Laser Induced Breakdown spectroscopy. It mentions two versions of Saha-...
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Concept of polarization in microwave rotational spectroscopy

I am trying to understand the concept of polarization of molecules after they are excited by a microwave pulse. The context is: The complexes are produced in a pulsed supersonic jet expansion of a ...
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What does the line strength mean in terms of spectral lines?

In my previous astrophysics lecture we were discussing the spectral types of stars. We were looking at the absorption features of dwarf stars in different spectral classes at a particular luminosity ...
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What does molecular term symbol $X^1\Sigma_u$ mean?

I'm confused about the molecular term symbol, for example:$X^1\Sigma_u$ mean. The super script $1$ and big $\Sigma$ was kind of like that of atomic term symbol. However, I'm not sure what does $X$ (...
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Plasma inside deuterium spectrum tube?

Hullo, In a deuterium spectrum tube there is a thin capillary in the middle (see picture) that glows purplish sort of. Now, I wonder what this glowing part actually consist of? Is it a completely ...
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Can the Standing Wave Ratio be deduced from a reflection spectrum?

The Standing Wave Ratio (SWR) is the ratio between the peak amplitude of the standing wave and the trough amplitude of the standing wave. I would like to figure out the SWR within a thin film when ...
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Why are stellar absorption line spectra passed through a cold gas?

I am currently studying spectral lines and saw in my notes that the way in which the absorbtion line spectra for a star was measured was by taking its light and shining it through a cold gas. The ...
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How to calculate the transition energy between $^2P$ to $^2S$ and $^2D$ to $^2S$ for sodium?

It's been known how to calculate the Zeeman effect. However how to calculate the transition energy between $^2P$ to $^2S$ and $^2D$ to $^2S$ for sodium($Z=11$)? ($^2P$ here meant term symbol ignored ...
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Principle series, Sharp series , Quantum defect, in Alkali Spectrum

Could anyone help me to understand the relation ship between principle series, Sharp series(https://en.wikipedia.org/wiki/Sharp_series ), electron spin, and atom's inner magnetic field etc. the ...
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How is “linewidth” defined for a damped driven oscillator?

Suppose we have a damped driven harmonic oscillator governed by the following equation of motion: $$\ddot \phi(t) + 2 \beta \dot \phi(t) + \omega_0^2 \phi(t) = J(t) \, .$$ In the case that $J(t) = A \...
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Which device to measure UV lamp wavelength with high precision

Which techniques and devices are able to measure the wavelength/frequency of a UV lamp within the wavelength range of 50nm - 300nm? Is a VUV Optical spectrometer the right device for this?
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Which colour comes out first from a prism?

When a narrow beam of white light is incident on a triangular prism. The speed of red light is maximum and violet is of minimum, red light bends less and travels less distance as compared to violet ...
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Selection rules in rotational spectroscopy- water molecule

The University of Liverpool maintains a ChemTube 3D page, where it says http://www.chemtube3d.com/spectrorotcd0-CE-TEST-ROTATE-ALL.html *> Highly symmetric polyatomic molecules, such as carbon ...
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Pressure inside spectrum tube?

I asked the firm who sells them here in Sweden, but they didn't know. I asked sellers on eBay, same answer. Is it different with say neon and hydrogen? Or is it the same pressure in all? I'm ...
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What's D lines for hydrogen like atom?

Could anyone tell me what's the definition of D lines for hydrogen like atoms? (Not just those two lines for sodium.)
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Pump Probe Spectroscopy using in ultrafast diffraction

I am going through currently the experiments on "Ultrafast Diffraction". Would you please explain with some significant degree of conceptual details how I can find the transverse Doppler shift ...
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Gamma from U238 decay chain

Where can I find detailed information on the gamma background from the U238 decay chain? Edit: Thank you for your replies. I need to find all the branching ratios and extract information of all the ...
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1answer
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difference between infrared radiation and infrared night vision

I need th eanswer that are infrared radiation and infrared night vision are same?. Are Infrared night vision camera use IR rays?, if yes then why we use Infrared LEDs around the lens??? I am totaly ...
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Experimental Assignment of Electronic Transitions in Atoms (Grotrian Diagram)

Grotrian diagrams often taught in instrumental methods of chemical analysis to chemists. After a decade, I finally found the original book of 1927 by Grotrian "Graphische Darstellung der Spektren von ...
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Is discharge tube dangerous?

Are those gas discharge tubes dangerous? I found atom spectra interesting, so I booked a 1.5 hour lab session at a local high school. The physics teacher gave me a few hydrogen tubes, helium tubes, ...
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What is line broadening phenomenon in quantum many body physics?

I have been reading Anderson's paper, "Absence of diffusion in a certain Random Lattice" and found the concept of inhomogeneous broadening. I couldn't really find a satisfactory explanation with a ...
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Why can't the electrons in Lamb-Retherford Experiment transition from 2S to 2P(j=1/2)

This experiment reveals metastable state and uses the fact that an electron in 22S1/2 can't go to the ground state as ∆l=0 is restricted. But I was thinking why doesn't electron go to 22P1/2 and then ...
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Does hydrogen reflect all visible wavelengths other than the wavelengths it absorbs?

I'm confused how reflection and absorption of photons work. For example hydrogen absorbs 4 wavelengths of light, but then that energy is emitted once the electron falls back to its ground state. So ...
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second-harmonic generation and inversion centers confined to a planar defect

Let's say that we have a phase which breaks inversion symmetry. Now lets say two domains of this phase meet at a plane such that the whole system now has inversion symmetry, with the inversion ...
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How can I determine, in what extent the fit to experimental data is good in Matlab?

I have experimental spectrum in which y-axis is intensity values, and x-axis is frequency values. Int - array of experimental intensities (y-axis). w - array of frequencies (x-axis). I know the view ...
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1answer
36 views

Light source needed in colorimeter and a spectrometer

I've found myself doing some research to ascert the differences when trying to assess the colour of a given sample. I've found two main options, which are (1) a colorimeter and (2) a spectrometer. ...
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1answer
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Predicting spectral lines

In the spectrum of some hydrogen-like ions the three lines are known, which belong to the same series and have the wavelengths 992, 1085, 1215 angstroms. What other lines can be predicted? I don't ...
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Fourier Coefficients

Suppose i've a two voice samples v1 and v2. Comparatively voice v1 is louder than the v2. If both the voice is spoken by the same person.(Spoken normally as he speaks) Is it good to state the ...
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What is the purpose of the slit in a spectroscope?

I built a spectroscope using a CD as diffraction grating. I understood how the grating works, but I didn't get why the slit is essential. Shouldn't it work even without the slit?
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How did Edwin Hubble estimate the velocity of distant stars?

I didn't know how to be succinct with my actual question in the title. My question is, how did he separate the components of the actual velocity of stars from that of the velocity due to recession (...
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Degenerate and Non-Degenerate Pump Probe Spectroscopy

I have just started my Msc Project, working on Pump Probe Spectroscopy. I will be most probably trying to setup a non degenerate pump probe technique, with the setup for degenerate type already done ...
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How was the electron in Rutherford's model producing a continuous spectrum and not a line spectrum?

How was the electron in Rutherford's model producing a continuous spectrum and not a line spectrum? What is the logical thinking behind that it will produce a continuous spectrum?
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What are good, reliable databases of atomic spectra?

I am looking for a database of atomic spectra, which contains atomic levels and their energies, electronic configurations, angular-momentum characteristics and lifetimes, and atomic transitions and ...
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Principle of Energy Dispersive x-ray Spectroscopy

I have a question about the EDS I don't understand how the detector can differentiate the Energy of incident x-ray simultaneously. In my thought, the emitted x-ray from the sample have different ...
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1answer
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Why sample is placed after the interferometer in FTIR?

In all image of schematics of FTIR I found (Wikipedia for example), the sample is placed after the interferometer: Wouldn't this miss some emergent effects, such photo-induced absorption, since the ...
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DIY IR spectrometry - stray light (higher orders diffraction maxima)

Context: homemade IR spectrometer with diffraction grating. Since $$m \lambda = d \sin \Theta _{m}$$ diffraction maxima of higher orders from shorter wavelengths will be mixed with lower order ...
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Crude spectrometer using the Huawei P20 monochrome sensor

I am thinking of taking advantage of the Huawei P20 Leica monochrome sensor to create a crude spectrometer to measure the spectrum of different light bulbs. I prefer not to use the optical ...
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133 views

Why do objects have a Natural Frequency? [closed]

Why should an object even have a natural frequency, why not vibrate at any other frequency? This just sounds nonsensical.
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Degeneracy of Polyatomic Molecules

I was given the following question to calculate in a problem class earlier this week: A volatile pure liquid comprising a single polyatomic molecule is placed in a sealed sample cell in an FTIR ...
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1answer
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Change in vibrionic energy in at atom at a higher excited electron state

I was studying the coupling of Vibrational and Electronic energies and was left confused at one aspect of the subject. Consider the image showing a transition from one electronic state to a higher ...
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Confusion regarding the possible term symbols/spectroscopic terms for (2p)(3p) configuration

Note: I have read this answer but it still doesn't address my question in terms of the permitted symmetry. I am learning about atomic states, and possible electron configurations. The first example ...
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Relative strengths of multipole contributions in atom photo-excitations

I have heard and read many times that dipole contribution to the photo-absorption matrix element is orders of magnitude stronger than quadrupole. To be exact, they are related as: $\frac{\langle ...
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1answer
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Vibrational and rotational spectroscopy

I don't understand why vibrational spectroscopy only has 1 intense absorption peak whereas the rotational spectroscopy has many separate peaks and the distance between the peaks is equal. $\Delta E\...
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2answers
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Variation of electronic energy levels $E_{nl}$ of a many-electron with $n$ and $l$

Within the central field approximation, the electronic energy levels $E_{nl}$ depend on both $n$ and $l$. For a given value of $n$, $E_{nl}$ increases with increasing value of $l$. For a given ...
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Is there a difference in the infrared absorption spectrum of a greenhouse gas when pure and when mixed with non-greenhouse gases?

According to the standard IPCC greenhouse climate change hypothesis a doubling of the preindustrial CO2 concentration of 285 ppm in the atmosphere - the current value is 405 ppm - would lead to an ...