Manipulation of slow molecular beams by static external fields.

Deflection by magnetic or electric field gradients has long been used to analyze or to alter the translational trajectories of neutral gas-phase atoms or molecules. Recent work has developed sources of slow, cold molecular beams that offer means to enhance markedly the attainable deflections, which are inversely proportional to the translational kinetic energy. The sensitivity and resolution can thus be much increased, typically by factors of 10(2)-10(4). We illustrate ways to exploit this enhanced deflection capability, particularly when balancing electric and magnetic deflections. Chemical scope can be greatly extended by utilizing feeble but ubiquitous interactions, especially the induced electric dipole due to the molecular polarizability and magnetic moments resulting from molecular rotation or nuclear spins. We also examine the effect of non-Maxwellian velocity distributions produced by supersonic expansions or by quantum statistics (pertinent for ultracold beams). Generic plots are provided, employing dimensionless variables, to facilitate the design and interpretation of experiments with deflections amplified by low kinetic energy.