Bose-Einstein condensation of lithium

Bose-Einstein condensation of Li-7 has been studied in a magnetically trapped gas. Because of the effectively attractive interactions between Li-7 atoms, many-body quantum theory predicts that the occupation number of the condensate is limited to about 1400 atoms. We observe the condensate number to be limited to a maximum value between 650 and 1300 atoms. The measurements were made using a versatile phase-contrast imaging technique. We discuss our measurements, the current theoretical understanding of BEC in a gas with attractive interactions, and future experiments we hope to perform.