Material characterization-UV-Vis-151208

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1、Material characteriza=on‐材料表征Molecular spectroscopy  Ultraviolet and visible spectroscopy (UV‐Vis) Circular dichroism (CD)芦红Tel: 83592767  Email: hlu@nju.edu.cn12/08/15Internal Energy of Molecules E=E+E+E+E+EtotaltranselecvibrotnuclE:electronictransitions(UV,X-ray)elecE:vibrat

2、ionaltransitions(Infrared)vibE:rotationaltransitions(Microwave)rotE:nucleusspin(nuclearmagneticnuclresonance)or(MRI:magneticresonanceimaging)2•RAMANSPECTRA-THISISALSOATYPEOFVIBRATIONAL-ROTATIONALSPECTRUM.ITISBASEDONSCATTERINGOFRADIATIONANDNOTONTHEABSORPTIONOFRADIATIONBYTHESAMP

3、LE.RAMANSPECTRAISOBSERVEDINTHEVISIBLEREGION.•NUCLEARMAGNETICRESONANCE(NMR)SPECTRA-THISTYPEOFSPECTRAARISESFROMTHETRANSITIONBETWEENTHENUCLEARSPINENERGYLEVELSOFTHEMOLECULEWHENANEXTERNALFIELDISAPPLIEDONIT.THEENERGIESINVOLVEDINTHESETRANSITIONSAREVERYHIGHWHICHLIEINTHERADIOFREQUENCYR

4、EGIONS.•ELECTRONSPINRESONANCE(ESR)SPECTRA-THISTYPEOFSPECTRUMARISEFROMTHETRANSITIONSBETWEENTHEELECTRONSPINENERGYLEVELSOFTHEMOLECULEWHENANEXTERNALMAGNETICFIELDISAPPLIEDONIT.3Electronic Spectroscopy •Ultraviolet(UV)andvisible(VIS)spectroscopy•Thisistheearliestmethodofmolecularspe

5、ctroscopy.•Aphenomenonofinteractionofmoleculeswithultravioletandvisiblelights.•Absorptionofphotonresultsinelectronictransitionofamolecule,andelectronsarepromotedfromgroundstatetohigherelectronicstates.4Electronic transi=ons Therearethreetypesofelectronictransitionwhichcanbecon

6、sidered;•Transitionsinvolvingp,s,andnelectrons•Transitionsinvolvingcharge-transferelectrons•Transitionsinvolvingdandfelectrons5NO 6VacuumUVorFarUV(λ<190nm)UV/VIS7Absorption-UV/VisibleBurningthingstoacrisp(asintheBunsenSpectroscope)cantellusabouttheatomscontainedinamolecule…But

7、thisdoesn’ttellusanythingabouthowthemoleculeisputtogetherFortunately,certainmoleculesabsorblightinacharacteristicway.Overtheyears,thishashelpedusidentifyandquantifybiologicalmolecules.8Absorption:PhysicalBasisAbsorptionoccurswhentheenergycontainedinaphotonisabsorbedbyanelectro

8、nresultinginatransitiontoanexcitedstateSincephotonandelectron