Spektroskopi

Pengantar Spektroskopi ELECTROMAGNETIC RADIATIONElectromagnetic radiation, or light, is a form of energy whose behavior is described by the properties of both waves and particles.Diffraction light as a waveInteract with matter light as a particle

Komponen medan listrik

An electromagnetic is characterized byKecepatanAmplitudoFrekuensi Sudut fasePolarisasiPropagasiWavelength Wavenumber

Particle Properties of Electromagnetic RadiationWhen a sample absorbs electromagnetic radiation it undergoes a change in energyThe interaction between the sample and the electromagnetic radiation is easiest to understand if we assume that electromagnetic radiation consists of a beam of energetic particles called photonsEnergy photons, E = h = h c/h= tetapan planck 6,62 x 10-34J.sElectromagnetic Spectrum

spektroskopiPhoton sebagai sinyalSecara umum dibagi 2Spektroskopi absorpsiSpektroskopi emisiSpektroskopi AbsorpsiThe energy carried by a photon is absorbed by the analyte, promoting the analyte from a lower-energy state to a higher-energy, or excited, state.

Absorbansi (A)The intensity of photons passing through a sample containing the analyte is attenuated because of absorption. The measurement of this attenuation, which we call absorbance, serves as our signalSpektrum Absorbansi

Emission Emission of a photon occurs when an analyte in a higher-energy state returns to a lower-energy state.Fotoluminesense: Emission following the absorption of a photonChemiluminesense: Emission induced by a chemical reaction

Basic Components of Spectroscopic InstrumentationSumber energyWavelength selectionDetectorsSignal processorEnergy sourceElectromagnetic sourceContinum: A source that emits radiation over a wide range of wavelengthsLine: A source that emits radiation at only select wavelengthsThermal energy sourceFlame: 2000 3400 KPlasma:gas panas terionisasi, 6000 10000 KChemical sourceKunang-kunang

Wavelength selectionFilter: colored glass, ex purple glass removes the complementary color green from 500560 nmMonokromatorFixed wavelengthscanning

14Interferometer

Detector Transducer: A device that converts a chemical or physical property, such as pH or photon intensity, to an easily measured electrical signal, such as a voltage or current

S = kP + DS = sinyal, P=power rem, D=dark currentTransducer Photon transducerPhototubes & photomultiplier : photosensitive surface absorbs UV, Vis, NIR radiation producing electric current proportional to number of photons reaching the transducerSemiconductor photodiode array Thermal transducer:The absorption of infrared photons by a thermal transducer increases its temperature, changing one or more of its characteristic propertiesSignal processor A device, such as a meter or computer, that displays the signal from the transducer in a form that is easily interpreted by the analystSpektroskopi serapanIn absorption spectroscopy a beam of electromagnetic radiation passes through a sampleAt selected frequencies, however, the radiations intensity is attenuated. This process of attenuation is called absorption.Two general requirements must be met if an analyte is to absorb electromagnetic radiation.Mekanisme interaksi antara rem dan analitEnergi harus sama dengan perbedaan energi antara keadaan energi analit terkuantisasiMekanisme interaksiFor ultraviolet and visible radiation, this interaction involves the electronic energy of valence electronsInfrared radiation, A chemical bonds vibrational energyE0 = ground electronic stateE1= first electronic excited state

Infrared Spectra for Molecules and Polyatomic IonsThe energy of infrared radiation is sufficient to produce a change in the vibrational energy of a molecule or polyatomic ion (see Table 10.1)Vibrational energy levels are quantized; that is, a molecule may have only certain, discrete vibrational energies. See Fic 10.14The energy for allowed vibrational modes, Ev

Vo = frekuensi vibrasi ikatan dasar, ditentukan oleh jenis ikatan misal C-C < C=CDv is 1 give rise to the fundamental absorption linesThe number of possible normal vibrational modes for a linear molecule is 3N 5 , for a nonlinear molecule is 3N 6UV/Vis Spectra for Molecules and IonsWhen a molecule or ion absorbs ultraviolet or visible radiation it undergoes a change in its valence electron configuration