\\DROBO-FS\QuickDrops\JB\PPTX NG\Droplets\LightingOverlay.png RAMANOVA SPEKTROSKOPIE \\DROBO-FS\QuickDrops\JB\PPTX NG\Droplets\LightingOverlay.png RAMANOVA SPEKTROSKOPIE • Prof. Chandrashekhara Venkata Raman Discovered the "Raman Effect“ – a light scattering effect in 1928, won the Noble Prize in 1930 for Physics •Ramam spectroscopy is the measurement of the wavelength and intensity of inelastically scattered light from molecules •The Raman scattered light occurs at wavelengths that are shifted from incident light by the energies of molecular vibrations •It is govern by the polarizability of electron cloud around the molecule \\DROBO-FS\QuickDrops\JB\PPTX NG\Droplets\LightingOverlay.png \\DROBO-FS\QuickDrops\JB\PPTX NG\Droplets\LightingOverlay.png \\DROBO-FS\QuickDrops\JB\PPTX NG\Droplets\LightingOverlay.png \\DROBO-FS\QuickDrops\JB\PPTX NG\Droplets\LightingOverlay.png CONDITIONS OF RAMAN SPECTROSCOPY •Vibrational modes that are more polarizable are more Raman-active: • •N2 (symetric stretch): cause no change in dipole moment – IR-inactive, but cause a change of the bond length (change the polarizability of the bond) - Raman-active. •CO2 (asymetric stretch): cause a change in dipole moment (IR-active), polarizability change by bond lengthering is canceled by asymmetric strecth (Raman-inactive). •Some bonds may be both IR and Raman active/inactive. \\DROBO-FS\QuickDrops\JB\PPTX NG\Droplets\LightingOverlay.png • Výsledek obrázku pro raman active vs ir active \\DROBO-FS\QuickDrops\JB\PPTX NG\Droplets\LightingOverlay.png laser UV 325 nm VIS 532 nm IR 785 nm Excitation efficiency high medium low Fluorescence high medium low Heat absorption low medium high