Lect06 - [Debye said to Schrdinger in 1925 that]to deal...

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History History [Debye said to Schrödinger in 1925 that]…to deal properly with waves, one had to have a wave equation. It sounded quite trivial and did not seem to make a great impression, but Schrödinger evidently thought a bit more about the idea afterwards. Just a few weeks later he gave a talk at the colloquium which he started by saying: "My colleague Debye suggested that one should have a wave equation; well, I have found one!" (Felix Bloch's eyewitness account Physics Today 28:12, 23–27 [1976]) "Erwin wrote to 'an old girlfriend in Vienna' to join him in Arosa. ... Efforts to establish the identity of this woman have so far been unsuccessful, since Erwin's personal diary for 1925 has disappeared. ... Whoever may have been his inspiration, the increase in Erwin's powers was dramatic.“ --W. Moore, Schr ö dinger
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Introduction to Quantum Physics: Matter Waves and the Schrödinger Equation
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Overview z Electron Diffraction particles as waves z Matter-wave Interference z Composite particles z Electron microscopy z Heisenberg Uncertainty Principle z Schrödinger Equation (SEQ) z Time dependent SEQ replaces F=ma (follow-up later) z Time-independent SEQ gives static solutions for wavefunctions z Physical interpretation of the wavefunction Midterm Exam next week will cover topics through Lecture 6, and will include Discussion, Homework and Lab topics through HW 3.
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electron gun Ni Crystal detector θ z In 1927-8, Davisson&Germer showed that, like x-rays, ELECTRONS can also diffract off crystals ! I( θ ) θ Interference peak ! 06 0 o Electrons can act like waves!! What does this mean? In discussion section: θ Matter Waves z DeBroglie (1923) proposed that, like photons, particles have a wavelength: Inversely proportional to momentum. We will see later that the discrete atomic emission lines also arise from the wavelike properties of the electrons in the field of the nucleus: Atomic hydrogen λ = h/p universal
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Double Double - - slit” Experiment for Electrons slit” Experiment for Electrons z Electrons are accelerated to 50 keV Æ λ = 0.0055 nm z Central wire is positively charged Æ bends electron paths so they overlap z A position-sensitive detector records where they appear. z << 1 electron in system at any time [A. TONOMURA (Hitachi) -- pioneered electron holography] Exposure time: 1 s 10 s 5 min 20 min Play Video: www.hqrd.hitachi.co.jp/em/doubleslit.cfm
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Act 1: Matter wavelengths z What size wavelengths are we talking about? Consider a photon with energy 3 eV, and therefore momentum p = 3 eV/c. Its wavelength is: ( ) ( ) nm s / m s . c eV s eV . p h 414 10 3 10 4 1 3 10 14 4 8 15 15 = × × × = × × = = λ z What is the wavelength of an electron with the same momentum? a) λ e = λ p b) λ e < λ p c) λ e > λ p
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Act 1: Matter wavelengths z What size wavelengths are we talking about? Consider a photon with energy 3 eV, and therefore momentum p = 3 eV/c. Its wavelength is: ( )( ) nm s / m s . c eV s eV .
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Lect06 - [Debye said to Schrdinger in 1925 that]to deal...

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