Introduction to Spectroscopy PDF

Introduction to Spectroscopy Prof. Manmohan Chhibber Department of Chemistry and Biochemistry [email protected] UCB009/24-25 ODD Sem  Spectroscopy To study changes in the property of light when it interacts with the m...

Introduction to Spectroscopy Prof. Manmohan Chhibber Department of Chemistry and Biochemistry [email protected] UCB009/24-25 ODD Sem  Spectroscopy To study changes in the property of light when it interacts with the matter. 2 UCB009/24-25 ODD Sem Electromagnetic Spectrum UCB009/24-25 ODD Sem Electromagnetic Radiation: Revision of fundamental Concepts Frequency (ν): It is defined as the number of times electrical field radiation oscillates in one second. The unit for frequency is Hertz (Hz). 1 Hz = 1 cycle per second Wavelength (λ): It is the distance between two nearest parts of the wave in the same phase i.e. distance between two nearest crests or troughs. The relationship between wavelength & frequency can be written as: c = ν λ As photon is subjected to energy, so E = h ν = h c / λ UCB009/24-25 ODD Sem How do we study changes in the properties of light when it interacts with matter? Detector Atoms Atomic Spectroscopy Molecules Molecular Spectroscopy UCB009/24-25 ODD Sem  What is Spectroscopy? It is the branch of science which deals with the study of interaction of electromagnetic radiation with matter. To know the molecular structure (Qualitative Analysis) To determine the quantity of species present (Quantitative Analysis) UCB009/24-25 ODD Sem  Types of Spectroscopies Atomic Absorption Flame Emission UV-Visible Fluorescence IR Phosphorescence Line spectrum Band spectrum UCB009/24-25 ODD Sem  Atomic Absorption & Emission Spectra E1 Excited State E1 Absorption Emission Process Process E hv hv E0 Ground State E0 UCB009/24-25 ODD Sem  Electromagnetic Radiation & Matter Interaction - Atoms Atomic Transitions  Electronic Transitions Line spectrum Intensity (A.U.)  Valence Electrons Absorption h Wavelength (nm) Ground State (E0 ) Emission h Excited State (E1) Ground state (E0) UCB009/24-25 ODD Sem Electromagnetic Radiation and Matter: Interaction Molecular Orbitals Molecular Transitions  Atomic Orbitals  Overlap Band spectrum Intensity (A.U.) Excited state Energy Wavelength (nm) Eelectronic Erotational Ground state Evibrational Note: This will be discussed in detail later during molecular spectroscopy UCB009/24-25 ODD Sem Observables in Spectroscopy In spectroscopy, we observe and measure the data from a spectrum of a sample consisting of atoms / molecules. What is a Spectrum ? Spectrum is a graph of the intensity of absorbed or emitted radiation by sample versus frequency (ν) or wavelength (λ).  How do we get the Spectrum? We get spectrum from a Spectrometer / Spectrophotometer. Spectrometer is an instrument used to measure / observe the spectrum of a sample. UCB009/24-25 ODD Sem UCB009/24-25 ODD Sem Thank You