CH 102 1st edition Lecture 27Outline of Current Lecture I. Bose-Einstein CondensatesII. Forming a Bose-Einstein CondensateIII. Laser CoolingCurrent LectureI. Bose-Einstein Condensatesa. A Bose–Einstein condensate is a state of matter of a dilute gas of bosons cooled to temperatures very close to absolute zerob. Under such conditions, a large fraction of bosons occupy the lowest quantum state, at which point macroscopic quantum phenomena become apparent.c. This state was first predicted, generally, in 1924–25 by Satyendra Nath Bose and Albert Einstein.d. In 1995 the first gaseous condensate was produced by Eric Cornell and Carl Wieman at the University of Colorado at Boulder NIST–JILA lab, in a gas of rubidium atoms cooled to 170 nanokelvin (nK).e. Wolfgang Ketterle at MIT shortly demonstrated important BEC properties. f. For their achievements Cornell, Wieman, and Ketterle received the 2001 Nobel Prize in Physics.II. Forming a Bose-Einstein Condensatea. The first "pure" Bose–Einstein condensate was created by Eric Cornell, Carl Wieman, and co-workers at JILA on 5 June 1995. b. They cooled a dilute vapor of approximately two thousand rubidium-87 atoms to below 170 nK using a combination of laser cooling and magnetic evaporative coolingIII. Laser Coolinga. A laser photon hits the atom and causes it to emit photons of a higher average energy than the one it absorbed from the laser. The energy difference comes from thermal excitations within the atoms, and this heat from the thermal excitation is converted into light which then leaves the atom as a photon. IV. Magnetic Evaporative Coolinga. Magnetic evaporative cooling also known as RF(Radio frequency)-induced evaporative cooling, is a technique for lowering the temperature of a group of atoms, pre-cooled by methods like laser cooling. To begin with, the process uses These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a magnetic field gradient to trap atoms in a magnetic trap, a flask-shaped confining potential. Collisions mean that over time, individual atoms will become much more energetic than the others, and they will escape the trap, removing energy from the system and reducing the temperature of the group remaining. This process, where particles by collision surmount a barrier, is similar to the familiar process by which standing water becomes water
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