  Supersonic beams of polar molecules are deflected using inhomogeneous
electric fields. The quantum-state selectivity of the deflection is used to
spatially separate molecules according to their quantum state. A detailed
analysis of the deflection and the obtained quantum-state selection is
presented. The rotational temperatures of the molecular beams are determined
from the spatial beam profiles and are all approximately 1 K. Unprecedented
degrees of laser-induced alignment $(<\cos^2\theta_{2D}>=0.972)$ and
orientation of iodobenzene molecules are demonstrated when the state-selected
samples are used. Such state-selected and oriented molecules provide unique
possibilities for many novel experiments in chemistry and physics.
