Person:

Patterson, David

Cold and dense samples of naphthalene ((C_{10}H_8)) are produced using buffer gas cooling in combination with rapid, high flow molecule injection. The observed naphthalene density is (n \approx 10^{11} cm_{−3}) over a volume of a few (cm^3) at a temperature of 6 K. We observe naphthalene–naphthalene collisions through two-body loss of naphthalene with a loss cross section of (\sigma_{\Lambda-\Lambda} = 1.4 × 10^{-14} cm^2). Analysis is presented that indicates that this combination of techniques will be applicable to many comparably sized molecules. This technique can also be combined with cryogenic beam methods to produce cold, high flux, continuous molecular beams.

Cold molecules promise to reveal a rich set of novel collision dynamics in the low-energy regime. By combining for the first time the techniques of Stark deceleration, magnetic trapping, and cryogenic buffer gas cooling, we present the first experimental observation of cold collisions between two different species of state-selected neutral polar molecules. This has enabled an absolute measurement of the total trap loss cross sections between (OH) and (ND_3) at a mean collision energy of (3.6 cm^{−1} (5 K)). Due to the dipolar interaction, the total cross section increases upon application of an external polarizing electric field. Cross sections computed from ab initio potential energy surfaces are in agreement with the measured value at zero external electric field. The theory presented here represents the first such analysis of collisions between a (^{2}\Pi) radical and a closed-shell polyatomic molecule.

We realize a continuous, intense, cold molecular and atomic beam source based on buffer-gas cooling. Hot vapor (up to 600 K) from an oven is mixed with cold (15 K) neon buffer gas, and then emitted into a high-flux beam. The novel use of cold neon as a buffer gas produces a forward velocity distribution and low-energy tail that is comparable to much colder helium-based sources. We expect this source to be trivially generalizable to a very wide range of atomic and molecular species with significant vapor pressure below 1000 K. The source has properties that make it a good starting point for laser cooling of molecules or atoms, cold collision studies, trapping, or nonlinear optics in buffer-gas-cooled atomic or molecular gases. A continuous guided beam of cold deuterated ammonia with a flux of 3×10(^{11}) ND(_{3}) molecules s(^{−1}) and a continuous free-space beam of cold potassium with a flux of 1×10(^{16}) K atoms s(^{−1}) are realized.

We demonstrate that buffer-gas cooling combined with laser ablation can be used to create coherent optical media with high optical depth and low Doppler broadening that offers metastable states with low collisional and motional decoherence. Demonstration of this generic technique opens pathways to coherent optics with a large variety of atoms and molecules. We use helium buffer gas to cool (^{87}Rb) atoms to below (7 K) and slow atom diffusion to the walls. Electromagnetically induced transparency in this medium allows for (50%) transmission in a medium with initial optical depth (D>70) and for slow pulse propagation with large delay-bandwidth products. In the high-(D) regime, we observe high-contrast spectrum oscillations due to efficient four-wave mixing.

The electric dipole moment of the electron (eEDM) is a signature of CP-violating physics beyond the Standard Model. We describe an ongoing experiment to measure or set improved limits to the eEDM, using a cold beam of thorium monoxide (ThO) molecules. The metastable (H) (^{3})(\Delta)(_{ 1}) state in ThO has important advantages for such an experiment. We argue that the statistical uncertainty of an eEDM measurement could be improved by as much as 3 orders of magnitude compared to the current experimental limit, in a first-generation apparatus using a cold ThO beam. We describe our measurements of the (H) state lifetime and the production of ThO molecules in a beam, which provide crucial data for the eEDM sensitivity estimate. ThO also has ideal properties for the rejection of a number of known systematic errors; these properties and their implications are described.

The authors realize a novel high flux source of cold atoms and molecules employing hydrodynamic enhancement of an effusive aperture at cryogenic temperatures. Molecular oxygen from the source is coupled to a magnetic guide, delivering a cold, continuous, guided flux of 3 1012 O2 s−1. The dynamics of the source are studied by creating and spectroscopically analyzing high flux beams of atomic ytterbium.

Cold and optically dense gases of atomic rubidium are produced using buffer gas cooling in combination with rapid, high-flow vapor injection. The observed rubidium density is 3 × 10(^{12})cm(^{−3}) at a gas temperature of ∼20 K, leading to an optical density of the order of 200.