Questions tagged [raman-spectroscopy]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0
votes
0answers
18 views

State coefficient in Kramer-Heisenberg-Dirac formula

I'm following the derivation of the Kramer-Heisenberg-Dirac formula from the book "Modern Optical Spectroscopy" and I'm having trouble understanding the wording and the derivation of the transition ...
0
votes
0answers
16 views

Is it possible to do Raman Spectroscopy without having to use a filter?

We are doing our thesis regarding Raman Spectroscopy and we saw that the setup usually includes a notch or edge filter. I understand that it is important in order to remove the Rayleigh scatter of the ...
2
votes
0answers
36 views

Why would $B_{1g}$ Raman mode still exist under $D_{4h}$ where $xx = yy$?

I come across some issues about Raman tensors under high symmetry , e.g. $D_{4h}$. A preliminary thought tells me that $x$ and $y$ are supposed to be equivalent in this point group therefore the Raman ...
0
votes
1answer
42 views

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 ...
0
votes
1answer
43 views

Raman effect and IR absorption

Let's consider a molecule with N atoms, on which is shot a polychromatic IR beam. From the quantum selection rules, we know that in a single event of absorption only one of the 3N-6 oscillators can be ...
1
vote
1answer
45 views

How to find out the temperature of phonons using the Raman anti-Stokes and Stoke intensities ratio?

Basically the title, the concept is simple, but I`m having a hard time trying to9 find an explicit solution.
1
vote
0answers
30 views

Why can't there be a direct absorption of a photon between Raman active states?

My question pertains to the fundamental difference between Raman spectroscopy and IR spectroscopy. Simply put, the Raman active transitions correspond to a change in the polarizability of the molecule ...
3
votes
1answer
190 views

How to determine if a calculated Raman mode in a crystal is active or not?

I have used an ab initio electronic structure code to calculate the harmonic Raman spectrum of a (molecular) crystal. However, no use of symmetry has been made, and it might well be that some of the ...
0
votes
1answer
56 views

How to explain about Raman spectroscopy?

What is the definition of Raman spectroscopy? How to explain in brief about antistoke line and Stoke line and Rayleigh?
0
votes
0answers
41 views

How are Maxwell equations satisfied when inelastic scattering occurs?

Consider two media, A and B (example air/dieletric). One finds conditions that the $\vec E$ and $\vec B$ fields must satisfy at the interface, namely $\hat n_\text{A-B}\times(\vec E_A-\vec E_B) = \vec ...
0
votes
0answers
49 views

Cannot observe Raman signal from Styrofoam

I am trying to build a low cost Raman spectrometer. I am using a refurbished B&WTek spectrometer that I purchased from eBay. I calibrated the unit myself and found to be very sensitive and ...
1
vote
0answers
85 views

Why is the Raman spectrum continuous?

A typical Raman spectrum looks something like this with peaks and a background. I would like to know (1) What is the reason for that background? (2) When I took spectra with quartz the background was ...
0
votes
0answers
52 views

How can I estimate the penetration depth of a laser in gallium oxide?

I am searching for a way to estimate the penetration depth of a laser with wavelength $\lambda$ in gallium oxide (Ga$_2$O$_3$) in a Raman setup, in order to know the depth at which I am probing. ...
2
votes
1answer
209 views

What is the difference between the dipole in IR and Raman vibrations?

In order for a vibration to be IR active, there must be a change in the dipole moment ($\mu$) of the molecule, which is given by: $\mu$ = $\sum$ q * r Where q is the charge magnitude and r is the ...
0
votes
1answer
41 views

How do I calculate the wavenumbers for a Broadband CARS system?

I had the question when I was reading a paper by Camp (High-Speed Coherent Raman Fingerprint Imaging of Biological Tissues), and I've been researching how to calculate wavenumbers from the 4 wave ...
1
vote
0answers
33 views

D-peak of Raman Spectra of Graphite explanation

The D peak in the Raman Spectrum of Graphite is attributed to the breathing mode of $A_{1g)$ symmetry involving phonons near zone boundary. The explanation is the following: The change of bond ...
-1
votes
1answer
341 views

Raman Scattering vs. Fluorescence (1-photon / 2-photon process) [duplicate]

I have a question considering the difference between Raman Scattering and fluorescence. I know that Raman Scataring is a non-resonant process, while fluorescence is resonant, that Raman scattering ...
-4
votes
1answer
58 views

Is there any good tutorial on how to read, convert and process .spc files using Python, R, Ruby, Java?

Is there any good tutorial on how to read, convert and process .spc files using Python, R, Ruby, Java? Need to extract content of 30 .spc vibrational spectroscopy files to do PCA and descriptive ...
0
votes
1answer
333 views

Lorentz distribution in emission peaks

Sometimes spectral peaks are fitted using a very pathological function named the Lorentz/Cauchy distribution. The Lorentz distribution has the property of not having a defined mean nor standard ...
2
votes
1answer
100 views

Classical treatment of Raman effect

I found the classical treatment of Raman effect as described here very intuitive and helpful considering I have no training in quantum physics. I have two related questions: 1) In absence of varying ...
-1
votes
2answers
178 views

How does Raman scattering not break energy quantization?

I understand how Raman scattering works and I understand that it can only be clearly explained if you think about light as a wave instead of a particle (otherwise you have to start talking about "...
0
votes
1answer
62 views

Time of re-emission of a photon in Raman scattering?

In Raman scatering events, when a photon is absorbed by a molecule, how much time(in average for small molecules) does it stay in the Virtual Energy State caused by the absorption.
0
votes
0answers
153 views

What does it mean if there's no peaks on raman spectrum?

I carried out Raman measurements of a doped semiconductor. I know what are the peaks of undoped one. I also know, that usually doped semiconductor has at least few peaks in similar positions to the ...
0
votes
0answers
197 views

How can electronic transitions in atoms contribute to the vibration of molecules?

In Raman spectroscopy, light is inelastically scattered from a sample and the shift in the scattered frequency (the Raman shift) is related to the vibrational modes of the sample. [...] and should ...
0
votes
1answer
483 views

Raman vs Fluorescence, scattering vs absorption, classical vs quantum [duplicate]

I am trying to grasp the difference between Raman scattering and fluorescence. To me it appears that the former is described in a somewhat more classical context as ordinary inelastic scattering, ...
1
vote
0answers
40 views

Understanding Depolarisation Ratio in Raman Spectroscopy

So the depolarisation ratio is given by the ratio of the scattered intensities \begin{equation} \rho = \frac{I_{\text{perpendicular}}}{I_\text{parallel}} \end{equation} My understanding of this is ...
2
votes
1answer
137 views

Which of these reasons are causes for the Stokes effect in Raman Scattering and/or Luminescence?

I’ve read several reasons for the Stokes effect and I can’t make out which of these are the true causes. Which of these apply to Raman or Luminescence or both? Are some of these the same thing? 1. ...
1
vote
1answer
301 views

Decoding the character table

The following is character table of water molecule I would like to know (1)What does the last 2 column in the table indicate? (2) How to deduce the functions in the last column?
0
votes
0answers
86 views

Do Raman spectra of crystals depend on stress, strain or both?

Very fundamental question. I always assumed that the spectra changes, because one changes the inter-atomic distances (strain) only. However, I am not sure this is the entire story. Does Raman ...
4
votes
0answers
503 views

Origin of Selection Rules for Rotational Raman spectra

I am aware of the fact that selection rules for transitions between two different quantum states, are obtained via an assessment of the corresponding transition matrix elements [1,2]. When we ...
1
vote
1answer
419 views

Baseline correction algorithm for Raman spectra. Raman baseline removal

Can someone please help with baseline correction algorithm? My task is to build an algorithm that normalizes baseline of spectrum WITHOUT using any additional software like Mathematica etc. I have a ...
4
votes
1answer
21k views

Second order spectra vs First order

Can someone explain for dummies what these are? How they are seen? And how to distinguish them? Perhaps, post some images. Thanks.
1
vote
1answer
1k views

Difference between polarizability and dipole moment

I am reading about Raman spectroscopy in general. And I learned that Raman spectra reflect the changes in the polarizability of a molecule, while the IR spectra reflect the changes in the dipole ...
4
votes
1answer
286 views

Laser speckle reduction for integration time of microseconds

How to reduce laser speckle noise for an imaging system that demands integration times of microseconds? I am aware of these two commercial solutions: Optotune laser speckle reducer. It has a ...
2
votes
1answer
307 views

Trace of raman tensors

A raman tensor $\gamma_m$ is defined as the derivative of the polarizability tensor $\alpha$ with respect to a raman mode $Q_m$, so $$ \gamma_m =\frac{\partial\alpha}{\partial Q_m} $$ $\gamma_m$ will ...
1
vote
1answer
144 views

Why are numbers not consistent? (Identifying phonon's frequency)

I am trying to connect several facts between each other to acquire a consistent picture. Fact 1. Monolayers of tungsten disulphide $WS_2$ have hexagonal crystal lattice, and the first Brillouin zone ...
1
vote
0answers
273 views

How one can count how many phonon modes is there in the crystal?

I'm reading the review on phonon and Raman scattering in 2D transition metal dichalcogenides (2D TMDCs). At the beginning of Section 2.1 it is said that, since there are two X-M-X units in the crystal'...
2
votes
1answer
672 views

Why is a notch filter required for Raman Spectroscopy?

It is my understanding that Raman Spectroscopy uses a notch filter (or sometimes an edge filter) to remove the light from the laser, so only the relevant Raman bands are present. However, if this is ...
2
votes
1answer
1k views

Why does Raman activity depend on polarizability?

Raman spectroscopy essentially records photoluminescence: (source) and a molecule is considered to be Raman active when there is a change of polarizability $\alpha$ (where $\mathbf{P}=\alpha \mathbf{...
1
vote
1answer
129 views

Why hydrofluoric acid (HF) has two Raman bands?

Hydrofluoric acid (HF) is a diatomic molecule with only one vibrational coordinate. Therefore I would expect only one Raman band, however there are two. Why? (source)
0
votes
0answers
34 views

Whether raman spectroscopy is dependent on crystallographic orientation

If I have three bars of Si, and each has the (100) (110) and (111) surface pointing up at the laser respectively, will I get a different raman spectra for each of them? In my opinion, I shouldn't ...
2
votes
0answers
49 views

What is the origin of the naming convention for the various branches in vibration-rotational spectroscopy?

In vibration-rotational spectroscopy, the different spectral lines are grouped into branches for different changes in the total angular momentum, i.e. $$ \begin{array}{rrrrrr} & \mathrm{O} & \...
16
votes
4answers
4k views

Why can't I see the blue color scattered by the lower atmosphere of the earth?

I understand that the blue colour of the sky is because of the scattering of blue light by molecules in earth's atmosphere. The scattering appears to be happening from molecules that are far above in ...
0
votes
1answer
120 views

Calculate complete function from imaginary part in raman response

When I want to calculate the raman response function $R$ from the molecular responses $g_a$ and $g_b$, I have to use the functions $$g_n(\Omega) = 2\gamma f_r\text{Im}\left[\tilde{R}_n\left(\Omega\...
0
votes
0answers
48 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 ...
3
votes
1answer
762 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 good ...
3
votes
1answer
4k 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 a ...
0
votes
1answer
682 views

What is the relationship between Raman peaks and phonon vibration modes?

I've seen Raman spectra, such as here, where peaks at certain wavenumbers were identified with phonon vibration modes (TO, LO, TA, LA). What is the relationship behind this, and how could I make such ...
0
votes
1answer
2k views

What is harmonic and fundamental bands in IR spectroscopy?

What is harmonic and fundamental bands in IR spectroscopy? I'm trying to find exact definitions. I guess that fundamental is $1\leftarrow 0$ transition (the most intense and energetic) and harmonic ...
0
votes
0answers
51 views

Raman amplification

Recently I read a bit about Raman amplification. Unfortunately, I did not understand everything. As far as I understood the resulting wavelength only depends on the pumping wavelength. Now I heard on ...