Atoms and Molecules Lecture Notes PDF

Module structure  Fundamentals of light  Propagation of light in waveguides  Light interaction with matter  Lasers  Photobiology basics  Biophotonics applications  Bioimaging  Tissue engineering  Topics to be covered  Atoms and Molecules  Molecular level...

Module structure  Fundamentals of light  Propagation of light in waveguides  Light interaction with matter  Lasers  Photobiology basics  Biophotonics applications  Bioimaging  Tissue engineering  Topics to be covered  Atoms and Molecules  Molecular level interactions  Absorption, spontaneous emission, stimulated emission  Fate of excited molecules  Fluorescence  Light scattering  Rayleigh, Mie, Raman, spectroscopy  At the start  ‘Indivisible’ particle – the atom  Making up different types of elements  ‘Plum pudding’ Democritus Wikipedia  Failures of Classical Mechanics  Classical Mechanics  Areas such as:  Blackbody radiation  Photoelectric effect  Discrete emission bands  Quantum Mechanics  Quantization of energy  Max Planck  whole multiples of  Revolutionary idea  Einstein – the photoelectric effect Planck's constant = 6.626068 × 10-34 m2 kg / s  Rutherford model  ‘Planetary model’ https://www.britannica.com/science/Rutherford-model/images- videos  Bohr model (1913)  Distances from the nucleus  Different energy  Radiation https://physicalsciencepaula.weebly.com/shellslevels.html  Electron transitions  Photon emission  Energy of the photon  E=hf  Discrete energy  Spectroscopy ν (Nu) = frequency P. Atkins and J. de Paula, Physical Chemistry 8th ed., Oxford University Press, 2006  Quantum Mechanics model  De Broglie - waves (1924)  Schrödinger's wave equations (1926)  Orbitals  High energy: Complex orbital shape https://courses.lumenlearning.com/chemistryatomsfirst/chapter/ development-of-quantum-theory-2/  Wave-particle duality of matter Matter Particle like behaviour Wave-like behaviour 1 Kinetic Energy  mv 2 h 2 Wavelength   mv Momentum mv Translational energy Quantized energy described by obtained through classical quantum mechanics mechanics Photons can behave like particles and electrons can behave like waves  Parts of the Atom  Atoms have electrons, protons and neutrons  Electrons (-) and Protons (+)  Same mass  ~1836 times lighter (rest mass)  # electrons = # protons  ‘ion’  ‘isotopes’  Filling orbitals with electrons Na Mg Al Si P S Cl Ar n=3 Li Be B C N O F Ne n=2 H He n=1 P. Atkins and J. de Paula, Physical Chemistry 8th ed., Oxford University Press, 2006  Orbital shapes 1s 2s 3s 3p 2p https://winter.group.shef.ac.uk/orbitron/ 3d  Allowed transitions in the Hydrogen atom  Spectral emission bands  Radiative electron transitions Numbers are given by 1/λ P. Atkins and J. de Paula, Physical Chemistry 8th ed., Oxford University Press, 2006  Molecular energies  Energies:  Electronic  Vibrational  Rotational  Translational  Quantized effects  Rotational movements  Electronic and vibrational energies  Molecular potential energy curve  Molecular potential energy curve  Equilibrium bond length Re  Minimum point of the energy curve P. Atkins and J. de Paula, Physical Chemistry 8th ed., Oxford University Press, 2006  Molecular vibrational states  Quantized vibrational states  Bond disassociation energy Do  Finite number of quantized vibrational energy states P. Atkins and J. de Paula, Physical Chemistry 8th ed., Oxford University Press, 2006  Typical normal vibrational modes CO2 H2O  Vibrational displacement  Linear: 3N-5 vibrational modes  Non-linear: 3N-6 vibrational modes  How many normal vibrational modes does a diatomic (e.g. H2) molecule have? v1 = symmetric stretch v2 = bending v3 = asymmetric stretch P. Atkins and J. de Paula, Physical Chemistry 8th ed., Oxford University Press, 2006  Summary  Energy is absorbed and emitted in discrete quanta; E = hf  Quantum mechanics is used to describe the electron orbital ‘shape’ in an atom  Electrons can transition between certain energy levels – absorbing or emitting a photon of equal energy in the process  A molecule’s bonds can bend and stretch as determined by its vibrational energy