  We demonstrate experimentally a method of all-optical selective rotational
control in gas mixtures. Using an optical centrifuge - an intense laser pulse
whose linear polarization rotates at an accelerated rate, we simultaneously
excite two different molecular species to two different rotational frequencies
of choice. The new level of control is achieved by shaping the centrifuge
spectrum according to the rotational spectra of the centrifuged molecules. The
shaped optical centrifuge releases one molecular species earlier than the
other, therefore separating their target rotational frequencies and
corresponding rotational states. The technique will expand the utility of
rotational control in the studies of the effects of molecular rotation on
collisions and chemical reactions.
