NASA Pursues Atom Optics to Detect Gravitational Waves

Why rubidium? If I recall correctly, rubidium was also used in the first Bose-Einstein condensate experiments. Does it have properties that make it especially useful for low-temperature physics?

This is just a $100K award (http://www.nasa.gov/offices/oct/stp/niac/niac_2012_phaseIand...), highly speculative, in an area (long-baseline interferometry) that has been explored by many groups.