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where Δν̃ is the Raman shift expressed in wavenumber, λ 0 is the excitation wavelength, and λ 1 is the Raman spectrum wavelength. Most commonly, the unit chosen for expressing wavenumber in Raman spectra is inverse centimeters (cm −1). Since wavelength is often expressed in units of nanometers (nm), the formula above can scale for this ...
In other words, it is the width of a spectrum curve measured between those points on the y-axis which are half the maximum amplitude. Half width at half maximum (HWHM) is half of the FWHM if the function is symmetric. The term full duration at half maximum (FDHM) is preferred when the independent variable is time.
The initial Raman spectrum is built up with spontaneous emission and is amplified later on. At high pumping levels in long fibers, higher-order Raman spectra can be generated by using the Raman spectrum as a new starting point, thereby building a chain of new spectra with decreasing amplitude.
In Raman and infrared spectroscopy, the selection rules predict certain vibrational modes to have zero intensities in the Raman and/or the IR. [11] Displacements from the ideal structure can result in relaxation of the selection rules and appearance of these unexpected phonon modes in the spectra.
A Fermi resonance is the shifting of the energies and intensities of absorption bands in an infrared or Raman spectrum. It is a consequence of quantum-mechanical wavefunction mixing. [ 1 ] The phenomenon was first explained by the Italian physicist Enrico Fermi .
Raman Tool Set is a free software package for processing and analysis of Raman spectroscopy datasets. It has been developed mainly aiming to Raman spectra analysis, but since it works with 2-columns datafiles (Intensity vs Frequency) it can deal with the results of many spectroscopy techniques.
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