  A strong inhomogeneous static electric field is used to spatially disperse a
supersonic beam of polar molecules, according to their quantum state. We show
that the molecules residing in the lowest-lying rotational states can be
selected and used as targets for further experiments. As an illustration, we
demonstrate an unprecedented degree of laser-induced 1D alignment
$(<\cos^2\theta_{2D}>=0.97)$ and strong orientation of state-selected
iodobenzene molecules. This method should enable experiments on pure samples of
polar molecules in their rotational ground state, offering new opportunities in
molecular science.
