  It is possible to tune the scattering length for the collision of ultra-cold
1S0 ground state alkaline-earth atoms using an optical Feshbach resonance. This
is achieved with a laser far detuned from an excited molecular level near the
frequency of the atomic intercombination 1S0--3P1 transition. Simple resonant
scattering theory, illustrated by the example of 40Ca, allows an estimate of
the magnitude of the effect. Unlike alkali metal species, large changes of the
scattering length are possible while atom loss remains small, because of the
very narrow line width of the molecular photoassociation transition. This
raises prospects for control of atomic interactions for a system without
magnetically tunable Feshbach resonance levels.

Atomic Physics