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Physicist delivers 'cool' presentation

Oct. 11, 2000



A Nobel Prize winner gave a lecture Tuesday in the Marrs McLean Science Building and impressed his audience by breaking frozen flowers, levitating magnets and demonstrating the laws of physics.

Dr. William D. Phillips' lecture was entitled 'Absolute Zero: The Story of Laser Cooling and Trapping.'

Phillips, who won the 1997 Nobel Prize in physics with Dr. Steve Chu and Dr. Claude Cohne-Tannoudji for his work with laser cooling, will speak in Chapel-Forum today.

He and his colleagues were able to drop the temperature of atoms to 700 nanokelvins above absolute zero, the coldest temperature ever reached by scientists. Absolute zero is the temperature when atoms stop moving.

Raheel Alam, a Socorro, N.M., freshman, came to the presentation because 'I heard we had a Nobel Laureate coming,' he said. 'Plus, I heard he was going to break stuff. And do you need a better reason than breaking stuff?'

Phillips used the experiments to show the process the scientists used to achieve their feat.

Laser cooling is the process used to slow atoms in order to make more accurate clocks for labs, whose accuracy is tested against the movement of cesium atoms.

It is done by utilizing the specific absorbency spectrums of atoms and then shifting that spectrum slightly so the atoms behave differently. The shift of the absorbency

spectrums causes the atoms to want to move toward certain frequencies of light and away from others. When lasers with a frequency slightly lower than the absorbency spectrum are circled with a group of atoms at the center of the circle, the effect of the lasers counteract each other and cause the atoms to slow down. This effect was termed 'optical molasses' by Chu.