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class37 - Potential energy curve for the particle Todays...

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Today’s class: Finish Radioactive decay • S canning T unneling M icroscope (STM) Quantum harmonic oscillator Potential energy curve for the α particle Nucleus (Z protons, & bunch of neutrons) New nucleus (Z-2 protons, bunch of neutrons) + Alpha particle (2 protons, 2 neutrons) Look at this systemelipsis as the distance between the alpha particle and the nucleus changes. KE Strong attractive force (Nuclear forces) V=0 for r barb2right As we bring the α particle closer to the core, what happens to potential energy? r Coulomb repulsion: r e e Z k r q kq r V ) 2 )( )( 2 ( ) ( 2 1 = = Nucleus: (Z-2) protons V(r) V(r) ~30 MeV Energy Large r: coulomb force dominates Small r: Nuclear force dominates r e e Z k r q kq r V ) 2 )( )( 2 ( ) ( 2 1 = = Review: Radioactive decay Edge of the nucleus (~8x10 -15 m), Nuclear (‘Strong’) force starts acting strong attraction between nucleons. Potential energy drops dramatically. r 1 to 10 MeV Wave function picture: ~1-10MeV of KE outside Exponential decay in the barrier V(r) Energy ~100MeV of KE inside the nucleus Wave function of the particle inside the potential well: Large KE barb2right small Wavelength Wave function of the free particle: Small KE barb2right Large wavelength Observations show Alpha-particles from the same chemical element exit with a range of energies.
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