  Photoassociation of ultracold atoms is shown to lead to alignment of the
product molecules along the excitation laser polarization axis. We
theoretically investigate pulsed photoassociation of $^{87}Rb$ atoms into a
specific weakly-bound level of the a $^3\Sigma_u^+$ metastable electronic state
and find both stationary and time-dependent field-free alignment. Although a
transform-limited pulse yields significant alignment, a frequency-chirped pulse
dramatically enhances the molecular formation rate at the cost of a slight
decrease in the alignment. Employing multiple pulses synchronized with the
vibrational and rotational periods leads to coherent enhancement of both
population and alignment of the target state.
