The use of electric multipole lenses for bending and focusing polar molecules, with application to the design of a rotational-state separator

The dipole interaction (Stark effect) of a polar molecule allows one to use an inhomogeneous electric field to bend and focus a neutral beam in a transport line. The dependence of the optics on the Stark potential energy is discussed and we describe the type of multipole-field lenses that are needed. The special features that differ from charged particle optics are discussed. The RMS envelope equations are used to design a rotational-state separator to be built at LBNL. Its performance is simulated using the non-linear trajectory equations (with off-energy molecules included) and we find good state selection.