Chapter12 - Quantum Theory Chap 12 Chemistry spectroscopic...

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Quantum Theory Chap 12 Chemistry spectroscopic techniques (composition and structure) Kinetics, electronic structure of atoms and molecules … … Quantum mechanic
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Classical Quantum Particle trajectory (position), momentum, energy are continuous and precise in mathematical sense. Any type of motion can be excited to a state of arbitrary energy Wave and particle are distinct different . The failure of classical physics (mechanics): Applied to very small particles: individual atom, nuclei, electrons, nanoparticles.- (how small is small?) Transfer of very small energy De Broglie relation (HW1)
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Force Field Field : function of position & time. Scalar field and vector field. Force field : a vector field indicating the magnitude and direction of force on object. Example: gravitational force field (act on mass), electric force field (acting on charge), magnetic field (acting on moving charge), pressure field. Force field is the interaction between objects. If objects move, then the field will be time dependent .
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The story of black body radiation All materials radiate EM wave when heated. Radiation occurs because the electrons are actively moving inside and constantly being accelerated. More short wavelength EM wave is radiated at higher temperature, may be associated with more vigorous movement of electrons. A black body is a body capable of adsorbing and emitting all wavelength. Black body can be approximated by a box with a pinhole.
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Black body radiation λ=? Nm (HW2) The contribution of shorter λ increases with temperature. Total emitted power increases with temperature. There is little radiation at very short wavelength (such as X- ray range) 1879 Josef Stefan established 1893 Wilhelm Wien ( Wien’s displacement law) 2.9 mm K
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Wein’s law: estimate the temperature of stars Example: the maximum emission of the Sun occurs at λ max = 490 nm, so its surface temperature must be close ? Example: Estimate the wavelength at the maximum energy Output of an incandescent lamp if the filament is at 3000 ? Stefan-Boltzmann law: A new ceramic materials that could be used as a filament At 3800 instead of 3000 . By what factor would the power output of a lamp using the new material increase?
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Classical theory Radiation from black body is the result of electron oscillating with frequency ν . The electron can oscillate and radiate at any frequency. Rayleigh-Jeans law It predicted correctly at long λ, but failed at short λ Ultraviolet catastrophe !!!
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Max Planck (German) – study black body radiation from view point of thermodynamics Energy of each electromagnetic oscillator is limited to discrete values and cannot be varied arbitrarily. e.g. oscillator of EM field corresponds to yellow light (ν), for example, could be stimulated only if a certain quantity of energy was provided. The limitation of the energy of an object to discrete values is called
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Chapter12 - Quantum Theory Chap 12 Chemistry spectroscopic...

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