Accession Number : ADA297024

Title :   A Quantum Gas of Cold Lithium Atoms.

Descriptive Note : Interim rept. 1 Jul 94-30 Jun 95,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE RESEARCH LAB OF ELECTRONICS

Personal Author(s) : Ketterle, Wolfgang ; Pritchard, David E.

PDF Url : ADA297024

Report Date : 29 JUN 1995

Pagination or Media Count : 11

Abstract : We have observed evaporative cooling of sodium atoms trapped in a spherical quadrupole trap. A novel technique, rf induced evaporation, was used to reduce the temperature by a factor of twelve and increase the phase space density by more than two orders of magnitude. The elastic collision cross section of cold sodium atoms in the F=1, m sub F=-l hyperfine state was determined to be 6 10(exp -12)sq cm which implies a positive value of the scattering length. The increase in phase space was limited by trap loss due to Majorana flops in the center of the magnetic trap where the magnetic field goes through zero. This trap loss is avoided in a novel hybrid trap employing magnetic fields and optical dipole forces. The magnetic field configuration is still the magnetic quadrupole, but the trap loss is suppressed by a tightly focused blue detuned laser beam which creates a repulsive AC Stark shift potential around the zero of the magnetic field. Evaporative cooling in this trap increased the phase space density by about five orders of magnitude, only a factor of 30 less than required to reach the phase transition to Bose-Einstein condensation. jg p.2

Descriptors :   *QUANTUM THEORY, *SODIUM, *COOLING, *GASES, *LITHIUM, *COLD FLOW, OPTICS, SCATTERING, LOW TEMPERATURE, MAGNETIC FIELDS, PHASE TRANSFORMATIONS, ELASTIC PROPERTIES, ALTERNATING CURRENT, ATOMS, QUADRUPOLE MOMENT, SPHERES, LASER BEAMS, LENGTH, CONFIGURATIONS, SHIFTING, CROSS SECTIONS, DIPOLES, HYBRID SYSTEMS, LOSSES, EVAPORATION, RADIOFREQUENCY, STARK EFFECT, COLLISIONS, CONDENSATION, PARTICLE COLLISIONS.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Atomic and Molecular Physics and Spectroscopy
      Quantum Theory and Relativity

Distribution Statement : APPROVED FOR PUBLIC RELEASE