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Control of the translational motion of methyl radicals is demonstrated by using pulsed magnetic fields created by a series of solenoid coils. By synchronously switching the magnetic fields corresponding to the motion of the radicals, we have observed the deceleration and focusing of a supersonic radical beam. The present result shows that Zeeman deceleration of polyatomic free radicals in the doublet state can be realized. This opens possibilities for trapping cold polyatomic free radicals in a spatially confined area leading to further studies of cold collisions and reactions.

We have demonstrated that supersonic beams of oxygen molecules (O2 ) in the ground rotational state were slowed to a near standstill by a linear Zeeman decelerator and successfully confined spatially in an anti-Helmholtz magnetic trap. The translational temperature o f the decelerated O2 molecules was about 800 mK. The demonstrated trapping capability of paramagnetic species opens up various possibilities for the investigation of cold collisions and reactions of various radicals in the sub-kelvin regime by spatially confining them in a magnetic trap.

We generate a continuous-wave (cw) cold methyl cyanide (CH(3)CN) beam by using an L-shaped bent quadrupole electrostatic guide (i.e., by a low-pass energy or velocity filtering), and use a photo-ionized time-of-flight mass-spectrometer method to experimentally measure and study the dependences of the longitudinal and transverse temperatures of the guided CH(3)CN beam and its guiding efficiency on the guiding voltage. We find a new scaling law: the longitudinal and transverse temperatures (T(z),T(rho)) of the guided CH(3)CN beam are proportional to the guiding voltage (T(z),T(rho) proportional to V(guide)), and further verify another scaling law: the molecular guiding efficiency eta is proportional to the square of the guiding voltage (eta proportional to V2(guide)). We also obtain some simulated results consistent with our experimental ones. We also measure the divergent angle of the output molecular beam and study its dependence on the guiding voltage. Our study shows that when the guiding voltage is V(guide) = +/-1 kV, a cw cold CH(3)CN beam with a longitudinal temperature of approximately 500 mK and a transverse one of approximately 40 mK can be generated by our L-shaped electrostatic guide. The divergent angle of the output CH(3)CN beam is about 16.4 degrees as V(guide) = +/-4 kV. It is clear that such a resulting cold molecular beam has some important applications in the fields of cold molecular physics, physical chemistry and chemical physics, etc.

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