Absorption Spectra Plot of Absorbance vs.v or called absorption spectrum Just as in emisson spectra an atom,ion or molecule can only absorb radiation if energy matches separation between two energy states Atoms: No vibrational or rotational energy levels-sharp line spectra with few features For example Na 3s->3p 589.0,589.6 nm (yellow) Na3s-→5p285.0,285.1nm(UV) Visible enough energy for valence (bonding)excitations UV and x-ray enough energy for core(inner)excitations Molecules: Electronic,vibrational and rotational energy levels-broad band spectra with many features AE=AEelectronie+AEvibrational +AErotational For each electronic state-many vibrational states For each vibrational state -many rotational states -→many features Absorption spectra affected by (1)number of atoms in molecule (2)solvent molecules more features blurred features CEM 333 page 2.7 Absorption Spectra Plot of Absorbance vs. n or l called absorption spectrum Just as in emisson spectra an atom, ion or molecule can only absorb radiation if energy matches separation between two energy states Atoms: No vibrational or rotational energy levels - sharp line spectra with few features For example: Na 3s®3p 589.0, 589.6 nm (yellow) Na 3s®5p 285.0, 285.1 nm (UV) Visible enough energy for valence (bonding) excitations UV and x-ray enough energy for core (inner) excitations Molecules: Electronic, vibrational and rotational energy levels - broad band spectra with many features DE = DEelectronic + DEvibrational + DErotational For each electronic state - many vibrational states For each vibrational state - many rotational states ®many features Absorption spectra affected by (1) number of atoms in molecule (2) solvent molecules more features blurred features CEM 333 page 2.7