Questions tagged [spectroscopy]

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

Filter by
Sorted by
Tagged with
1
vote
1answer
36 views

Selection rules in neutron scattering

Why doesn't neutron scattering have selection rules? According to Wikipedia, it seems that the value of the transition moment integral will be non-zero, but I guess another way of phrasing my question ...
0
votes
0answers
9 views

Four-wave mixing and modulation transfer spectroscopy: why do sidebands appear on the probe?

I'm trying to understand modulation transfer spectroscopy in simple terms. For those unfamiliar with it, this article gives a very good summary. To sum it up, two counterpropagating beams, a pump and ...
1
vote
1answer
23 views

Why does infrared spectroscopy require a change in the dipole moment?

An infrared signal is generated due to fluctuations in the permanent dipole moment, but can an infrared signal be induced in a molecule due to a change in the quadrupole moment?
2
votes
1answer
49 views

What is the peak lineshape in spectroscopy?

I have two questions regarding the lineshape of peaks in spectra obtained with detectors (such as germanium detectors) in spectroscopy. What we often read is that the detector's response lineshape ...
0
votes
0answers
13 views

What is the effect of a supermassive black hole at the centre of the galaxy on this galaxy's spectrum?

After analysing the spectrum of the spiral galaxy (featuring flat rotation curve) we are asked to draw a sketch showing the effect on the galaxy spectrum if the galaxy were to have a supermassive ...
1
vote
1answer
15 views

Spectroscopy of mixed material

If there is an unknown sample $X$ consisting of various molecules, is there a general method to determine the molecules making up the sample using spectroscopy? Details. This is my naive guess on how ...
2
votes
1answer
31 views

Absorption spectroscopy - transmittance (normalized)

In the absorption spectroscopy we can calculate transmittance $T$ of a given sample by comparing how the intensity of the incident beam $I_{0}$ is decreased with the distance (Lambert-Beer Law). $A = -...
1
vote
1answer
78 views

How can the limited to infrared James Webb space telescope do spectroscopy of the exoplanets' atmosphere without seeing in the visible spectrum?

image source: https://www.youtube.com/watch?v=bI-JIAmiL7A JWST will look for the composition of exoplanets' atmosphere using the spectroscopy method. However as far as I know for elements of the ...
0
votes
0answers
20 views

Spark chamber spectrometer in Cronin and Fitch experiment

I'm currently studying Cronin and Fitch experiment that showed the indirect CP-violation. I understand the physics behind it and how the experiment was done, but while trying to go deeper into the ...
0
votes
0answers
17 views

Quantum numbers for ${}^3P_2$ State of trivalent Praseodymium ion

I am trying to understand energy states in the Pr3+ Ion. The ground state is 3H4, which can only be achieved by giving the two electrons in the 4f-orbital the magnetic quantum numbers ml=2,3 or ml=-2,-...
0
votes
1answer
23 views

Spectrum features in an atmosphere with temperature inversion

Consider an atmosphere with a temperature inversion (cooler on the bottom and hotter on the top). Imagine the hottest one emit as a blackbody. Would we see any absorption/emission lines?
1
vote
0answers
10 views

Why refer to Near Infrared Reflectance Spectroscopy (NIRS) while using a much wider spectrum (350-2500 nm)?

I am puzzled about the way a method names vs. specificity of the method differ in the literature around spectroscopy applications. A very widely used field spectroradiometer, recording reflectance ...
0
votes
0answers
17 views

Light with uniform spectograph?

I've been looking for lights, namely LEDs as they seem to be a more controlled and reliable method of producing light (at least from my degree of familiarity), that can produce light at a very ...
2
votes
0answers
74 views

Franck-Hertz experiment

In the Franck-Hertz experiment why are the peaks much sharper than the troughs? Also our data analysis suggested that the distance between the peaks is smaller (nearer to $4.9 \ $ eV ) than the ...
1
vote
1answer
37 views

A spectrum of a mild temperature object

If I was to measure a spectrum of my palm, how would it look like? WIll it be continuous? Will it be possible to identify the components the palm is made of by digesting the spectrum?
-2
votes
1answer
91 views

If the sky is full of microwave radiations then why don't we see it?

So basically we know that the sky is full of microwave radiations but why can't we see it if so ?
0
votes
0answers
35 views

Integrate the expression of error for photometric galaxy clustering and after compute the variance of shot noise

The error on photometric galaxy clustering under the form of covariance which is actually a standard deviation expression for a fixed multipole $\ell$ : $$ \sigma_{C, i j}^{A B}(\ell)=\Delta C_{i j}^{...
0
votes
0answers
23 views

Spectral energy density and energy content per normal mode

How can I see that a spectral energy density given by a cubic law $$ \rho(\omega)=\frac{\hbar}{2\pi^2c^3} \omega^3 $$ has the property that the average energy content per normal mode is $$ \mathcal{E}...
0
votes
1answer
31 views

How bright a light should be to be considered in part of atomic spectrum?

I've been doing atomic spectrum experience, and besides the major peaks, there are many little bumps shows up. I looked up for an official one, found that they only shows the major peaks on the ...
0
votes
0answers
21 views

Notation for molecular vibrational levels and population inversion

How do I interpret the notations (e.g. (0 0$^0$ 1)) for molecular vibrational levels like in the following diagram for CO$_2$? Also, since one can excite multiple quanta of the same vibrational mode, ...
1
vote
2answers
75 views

Is my understanding of the limitations of the Bohr model related to atomic spectra correct?

I'm talking about a neutral hydrogen atom here: According to Bohr, if the electron jumps from $n=2$ to $n=1$, there'd be only one wavelength of light being emitted. However, that is not the case we ...
1
vote
0answers
46 views

Identifying the spectral lines of helium

I have recently performed an old experiment using a spectrograph with a photographic film having a helium spectral lamp as a source of light. The picture attached below shows the developed photo of a ...
0
votes
1answer
88 views

Grotrian diagram for Helium

Hi, is this Grotrian diagram for helium wrong? I can't understand how a $1s2d$ state is possible since my understanding was that the $d$ states only start at $n=3$?
0
votes
0answers
35 views

What do chi ($χ$), psi ($ψ$), and capital gamma ($Γ$) stand for in these equations about molecular geometry (combination bands and overtones)?

Special case If one of the symmetries is doubly degenerate in the excited state a recursion formula is required to determine the symmetry of the $v$th wave function, given by, $$\chi _{v}(R) = \frac{1}...
1
vote
0answers
22 views

Absorption rate vs. Einstein Absorption Coefficient

I am trying to understand the absorption rate (or absorption probability density), which is defined as $$p_{ab}=\frac{\sigma c}{V}, $$ where $\sigma$ is absorption (transition) cross section and $V$ ...
2
votes
2answers
83 views

Hydrogen line spectrum [closed]

lately I have come across the hydrogen line spectrum, I quite understand it as I could easily solve all numerical questions. However, conceptually I feel stuck at two points. If an electron absorbs ...
0
votes
0answers
24 views

Why are molecular orbitals HOMO and LUMO invariant under spin flip?

Atomic theory says singlet and triplet energies for the same orbital differ because of exchange interaction. However, molecular orbital (MO) theory describes the energy between the HOMO (highest ...
1
vote
3answers
52 views

What are the advantages of radio spectroscopy? [closed]

What is the main purpose for radio spectroscopy? What information of the atomic structure of atoms can we gain from using radio frequency radiation rather than X-rays? Since the wavelength of radio ...
2
votes
1answer
59 views

Direct experimental observation of magnetic orbital quantum number $m_l$

Is there an experimental way to observe magnetic quantum number $m_l$ values directly, the way electron spin was detected by Stern Gerlach experiment or proton's spin by nuclear magnetic resonance ...
10
votes
1answer
569 views

Why do different atomic isotopes have different atomic spectrums?

We know that different elements have different atomic spectrums as a result of the difference in charge and electron shielding that occurs when extra protons are added to a nucleus. We also know that ...
0
votes
1answer
16 views

Pumping laser for Ti:Sapphire laser

I now own Tsunami Ti: Sapphire laser from Spectra-Physics. This laser is an ultrafast laser. Now, this is pumped by Millenia CW green laser. Apart from the output coupler problem, I am considering ...
0
votes
0answers
8 views

Does the inelstic mean free path change with the doping concentration?

Does the bulk plasmon cross section depend on the doping concentration? I measured EELS for three different doping concentrations of silicon and the inelstic mean free path seems to increase ...
2
votes
1answer
23 views

Determining the frequency of a monochromatic light source from measurements of irradiance alone?

Let's say we have a monochromatic source of unknown frequency (say, a laser) and some device/sensor that measures the total photon energy absorbed over a fixed time interval (essentially, irradiance). ...
1
vote
1answer
33 views

Sodium Energy and Angular Momentum of Electrons

In a sodium atom, why do the $s$ and $p$ angular momentum states drop to the $3p$ rather than straight to $3s$ ? (See the energy level diagram below.)
3
votes
1answer
154 views

Why does the fringe contrast disappear for a divergent beam (FTIR using a Michelson Interferometer)?

I am reading "Fourier Transform Spectroscopy" by Griffiths and Haseth. In section 2.6 Effect of Beam Divergence, the authors state that: When the extreme ray is out of phase with the central ...
3
votes
1answer
46 views

Absorption and emission spectra - regarding excited state of electrons

I had a question regarding the "excited state" of electrons. I know that electrons can jump up from their ground state to higher energy levels if given a specific amount of energy. But what ...
0
votes
0answers
35 views

Trying to calculate the Full Width at Half Minimum of a certain potential

I am calculating the Full Width at Half Minimum of several potentials. I came across a potential that has the following form: Points a and b are the local maxima of the curve. Point e is the minimum ...
0
votes
0answers
9 views

Quantum numbers and terms - emission spectroscopy

I was trying to analyze some emission spectroscopic data and I encountered unfamiliar notation of the terms for me. The electronic states of the atoms can be described by quantum numbers using the ...
1
vote
0answers
27 views

Corrections to energy levels in many-electron atoms

While I've been solving the Hydrogen atom problem, using quantum mechanics, I came across several correction factors, that give rise to the fine structure of the hydrogen spectrum. The Hamiltonian can ...
0
votes
0answers
28 views

Calculate energy levels from term symbols

Term symbols offer an extremely compact way of describing the different energy levels of a system. It takes into account many corrections, including the central field, spin-orbit interaction, and ...
0
votes
0answers
21 views

Question on calculation of refractive index and extinction coefficient from relflection and transmittance data

I have reflection (R) and transmittance (T) data and I want to calculate refractive index (n) and extinction coefficient (k) from these data. But I have taken the reflection spectra at 45 degree angle ...
1
vote
1answer
35 views

Pressure broadening in absorption spectra

I was reading about pressure broadening for atomic spectra. What I can't understand is why it is important in absorption spectra if the collisions affect only the lifetime of the excited states. It ...
0
votes
1answer
38 views

Total number of states for a two electron system

Let's say, I have the following electronic configuration, $1s2s$, and I'm trying to find all the possible states. By looking at the configuration, it is obvious, that in the $|l_1,m_{l_1},m_{s_1},l_2,...
0
votes
0answers
45 views

Triplet states and Fine Structure

If we have a system, with total spin angular momentum given by $S$, then we have spin multiplicity equal to, $2S+1$. This spin multiplicity basically tells us the different spin states, this system ...
0
votes
1answer
43 views

Atomic levels energy

While reading about $LS$ coupling, and the fine structure of atomic energy levels, of various electron-electron configurations, I came across two different representations. For example, if we consider ...
2
votes
0answers
86 views

Degeneracy of Atomic energy levels

I've started reading about the atomic spectra and came across LS coupling and so on. However, I have a doubt regarding the entire thing. Let us say, we have 2 electrons, say $4p-4d$ state, and we are ...
0
votes
0answers
12 views

Sloan Digital Sky Server (SDSS) spec file headers

I downloaded a FITS file of spectra from the Sloan Digital Sky Server (SDSS), I am not getting that why there are more than one BinTableHDU for spectra? Is this because the same star is observed at ...
0
votes
0answers
24 views

Detailed balancing not upheld?

Is line saturation, whereby a line excited due to the transition between two states does not increase in intensity, an example of detailed balancing not being upheld? Detailed balance is the condition ...
0
votes
1answer
25 views

Do all of the energy levels listed in Hydrogen Spectral Series assumed to be s ('sharp') sublevels?

When reading about the hydrogen spectral series (Lyman, Balmer, etc.) I noticed that nowhere are suborbital or sublevels (azimuthal) mentioned; only principal quantum numbers n .... Are there any p or ...
0
votes
1answer
52 views

How is number of photons found on a spectra?

Sorry for the stupid question, but I am very new to this and have no background in physics. Say we have a spectra as the one in the image, which represent a charge distribution over a specific channel,...

1
2 3 4 5
18