Midterm exams I
... 2. What information do you get from a Raman spectrum?
3. What is the vibrational frequency of a diatomic molecule?
4. Where would be Raman lines (in cm-1 ) for (1) diamond and (2) for helium?
5. Which molecule would have higher vibrational frequency: Fluorine (F2) or iodine
6. Why Raman spectr ...
... - Raman does not “see” many common polar solvents can
use with aqueous samples – advantage over IR
slides introducing IR/Raman of proteins
... sample. What we seek to understand is:
– the RATE at which the molecule responds to this
perturbation (this is the response or spectral intensity)
– why only certain wavelengths cause changes (this is the
spectrum, the wavelength dependence of the response)
– the process by which the molecule alters ...
... •Arm waving explanation, you can get Raman intensity if the
vibration of the atoms causes a change in the polarization of the
electron density at the macro scale. Of course every vibration of
an atom causes a change in the polarization of the electron density
at the atomic scale.
•Important case, if ...
39 Raman Scattering Spectroscopy Raman - Rose
... The induced dipole therefore varies in two ways; the strength of the induced dipole
varies with the electric field, and the strength of the induced dipole varies with
molecular vibration. Oscillating dipoles emit radiation at their frequency of
oscillation, with an intensity proportional to (m´)2. T ...
Problem Set 1 (due 2/21/06)
... directed into a monochromator for scanning the emission.
A fluorescence excitation spectrum is collected by measuring the intensity of a
single emitted wavelength over a scan of excitation wavelengths. Typically the
source would be a continuous source with a monochrometer (or the harmonics of
a tuna ...
Fourier Transform IR Spectroscopy
... • Fourier-transform infrared spectroscopy is a vibrational
spectroscopic technique, meaning it takes advantage of
asymmetric molecular stretching, vibration, and rotation of
chemical bonds as they are exposed to designated
wavelengths of light.
• Fourier transform is to transform the signal from the ...
Stimulated Raman Spectroscopy 1 1. Introduction
... a cell that was connected to a listening tube. When the sunlight was repeatedly blocked and unblocked, sound could
be heard through the listening tube at the sunlight chopping frequency. The technique saw few applications until
about 1968 when a rise in its use began due to the availability of laser ...
5 - www2
... Here the coordinate Q = Q0 exp(iωvibr ·t) describes the internuclear displacement. Inserting α into μ
shows that the scattered radiation now also includes Raman shifted frequencies with ω0 ± ωvibr. The
intensity of these lines depends on ∂α/∂Q.
Resonance Raman scattering. In the Raman (R) scattering ...
... 4. If the spectra are "noisy" you can increase the integration time, but the program seems to
go crazy if you choose integration times >200 sec. To get longer "runs", you can export
the data from several runs and combine them using Excel or IGOR.
5. Save your spectra (on a memory key or floppy) for ...
BJ - Faculty Web Pages
... could you do to the sample to increase the intensity of the spectrum? Explain.
Heat the sample. Most molecules do not change frequency upon scattering
(Rayleigh). Even fewer molecules undergo anti-Stokes scattering, as these lines
originate from lower populated excited states. By heating the sample, ...
... from the superradiant threshold. As such, it merely is a
limiting case of previously known treatments of superradiance. Two additional new findings of the Letter
are incorrect: (1) the claim that adiabatic elimination of
the excited state of the atoms is only possible when the
probe pulse propagates ...
LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
... 16 a. Explain, with theory the spectrum of a linear diatomic molecule of rigid rotor type.
Outline the correction for non-rigid type. (10.5)
16 b. The rotational constant of NO is 1.7201 cm-1. Calculate the moment of inertia of the
molecule about a line perpendicular to its axis. (2)
17 a. Outline b ...
Raman Spectroscopy - University of Arizona
... state to the lowest electronic
state. E = h * ν = h * (c / λ) where
the energy is equal to plank’s
constant multiplied by the
frequency of the light which is
nothing but the velocity of light
divided by its wavelength. This
suggests that a light source with
the longest possible wavelength
would be i ...
Dr - srldc
... includes all these colors. When a beam of sunlight is passed through a glass
prism a patch of these *color- bands are seen. This is called the spectrum. The
Spectro- meter is an apparatus used to study
CV Raman Life and Work
... 1922- Molecular diffraction of light: What would happen in a black body enclosure if
the exchange of energy took place by molecular scattering? How energy could be
transferred between quantum of light and molecules?
1923- Theory of viscosity
1293- Scattering of Sun light by water (not because of wea ...
... Raman scattering is a two-photon linear inelastic light scattering process. The elastic
counterpart is the well-known Rayleigh scattering process. In spontaneous Raman scattering
the light is emitted in random directions (although for polarized light there may be preferred
directions, depending also ...
18.1 Raman Scattering
... 18.1 Raman Scattering
• an energy level diagram shows four types
of scattering processes
• Rayleigh scatter is due to microscopic
refractive index changes, while Raman
scatter is due to time-dependent changes
• scattering cross-sections are used to
compare signal strengths from Ray ...
Resonance Raman spectroscopy
Resonance Raman (RR) spectroscopy is a name given to Raman spectroscopy when the incident laser frequency is close in energy to an electronic transition of a compound or crystal under examination. The frequency coincidence (or resonance) can lead to greatly enhanced intensity of the Raman scattering, which facilitates the study of compounds present at low concentrations.Raman scattering is usually extremely weak, of the order of 1 in 10 million photons that hit a sample are scattered with the loss (Stokes) or gain (anti-Stokes) of energy because of changes in vibrational energy of the molecules in the sample. Resonance enhancement of Raman scattering requires that the wavelength of the laser used is close to that of an electronic transition. In larger molecules the change in electron density can be largely confined to one part of the molecule, a chromophore, then the Raman bands that are enhanced are primarily from those parts of the molecule in which the electronic transition leads to a change in bond length in the excited state of the chromophore. For large molecules such as proteins, this selectivity helps to identify the observed bands as originating from vibrational modes of specific parts of the molecule or protein, such as the heme unit within myoglobin.