We describe a device using the Stark effect to extract the cold fraction of nitric oxide molecules from a warmer thermal distribution. Room temperature NO is cryogenically cooled to 72-82 K and injected into a straight, hexapole guide that uses the Stark effect. By blocking line-of-sight trajectories from the input to the output, primarily the slowest molecules are guided around the obstruction and are transferred into a new chamber. We measure the temperature distribution using a field-stabilized Rydberg time-of-flight technique. A superposition of molecular Rydberg states is excited, sufficiently increasing the lifetime of the excited state for a time-of-flight measurement for cold molecular samples. We produce a continuous source of nitric oxide with temperatures ranging from 7 to 20 K in the lowest ro-vibrational state. The output temperature is controlled by the initial temperature distribution and the guide voltage.
I present the experimental results of a new source of cold molecular production using activated carbon and the design of the necessary apparatus. This new source may eliminate the need for laser ablation loading in buffer gas cooling experiments. I also analyze the relative signal amplitude of rotational lines of cold Nitric Oxide (NO) molecules in its lower fine structure state. Experimental results showing the effects of the hexapole velocity filter on the production of lowest ro-vibrational low field seeking states of a cold molecular sample of NO is also discussed. The sample is produced by the extraction of the cold fraction of the Maxwell-Boltzman distribution of a thermal source.
Recently we developed a technique for producing cold molecules from a supersonic molecular beam via single collisions with a supersonic atomic beam [M. S. Elioff, J. J. Valentini, and D. W. Chandler, Science 302, 1940 (2003)]. This cooling technique necessarily produces the cold molecules at the relatively high density crossing of the atomic and molecular beams. In previous reports, secondary glancing collisions with the remnant atomic and molecular beams lead to rapid depletion of the cold molecules limiting the observation time to less than $10\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{s}$ with an estimated temperature of
440mK. Here we present experimental conditions for the kinematic cooling technique which overcome the limitations of the previous experiments. We demonstrate the success of this experiment for the production of cold nitric oxide (NO) in the ground vibrational,
j=7.5 rotational, state in order to compare with our previously reported data. With the present setup, we are able to extract the cold molecules from the pulsed molecular and atomic beams and we observe these cold
NO(X)j=7.5 persisting for over $150\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{s}$. This long observation time demonstrates our ability to temporally and spatially separate the cold molecules from the parent atomic and molecular beams, simultaneously allowing for a better measurement of the final average velocity for the kinematically cooled molecules. From the data we find a final average velocity of the
NO(X)j=7.5 of approximately
4.5m∕s, consistent with simulations. The final observed average velocity is equated to a temperature of approximately
35mK, over an order of magnitude colder than our previous measurements.
We report the cooling of nitric oxide using a single collision between an argon atom and a molecule of NO. We have produced significant numbers (108 to 109 molecules per cubic centimeter per quantum state) of translationally cold NO molecules in a specific quantum state with an upper-limit root mean square laboratory velocity of 15 plus or minus 1 meters per second, corresponding to a 406 plus or minus 23 millikelvin upper limit of temperature, in a crossed molecular beam apparatus. The technique, which relies on a kinematic collapse of the velocity distributions of the molecular beams for the scattering events that produce cold molecules, is general and independent of the energy of the colliding partner.
As part of an ongoing investigation of cold-molecule collisions involving nitric oxide (NO), we here theoretically assess the first- and second-order perturbation-theory approximations to the Stark shifts; such approximations have been used almost exclusively in previous published research on NO in external electric fields. We perform this assessment by comparison to Stark shifts from the corresponding nonperturbative two-state model, considering field strengths from zero to values typical of current experimental studies of cold molecules. To facilitate the future use of this model, we give expressions for the Stark energies in a generic form that can trivially be applied to any molecules in the class under consideration. To provide insight into the validity of the two-state model, we also experimentally assess the two-state Stark shifts for NO.
We report the cooling of nitric oxide molecules in a single collision between an argon atom and an NO molecule at collision energies of 5.65 {+-} 0.36 kJ/mol and 14.7 {+-} 0.9 kJ/mol in a crossed molecular beam apparatus. We have produced in significant numbers ({approx}10{sup 8} molecules cm{sup -3} per quantum state) translationally cold NO({sup 2}{Pi}{sub 1/2}, {nu}' = 0, j' = 7.5) molecules in a specific quantum state with an upper-limit laboratory-frame rms velocity of 14.8 {+-} 1.1 m/s, corresponding to a temperature of 406 {+-} 28 mK. The translational cooling results from the kinematic collapse of the velocity distribution of the NO molecules after collision. Increasing the collision energy by increasing the velocity of the argon atoms, as we do here, does shift the scattering angle at which the cold molecules appear, but does not result in an experimentally measurable change in the velocity spread of the cold NO. This is entirely consistent with our analysis of the kinematics of the scattering which predicts that the velocity spread will actually decrease with increasing argon atom velocity.