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Aluminum monochloride (AlCl) has been proposed as a promising candidate for laser cooling to ultracold temperatures, and recent spectroscopy results support this prediction. It is challenging to produce large numbers of AlCl molecules because it is a highly reactive open-shell molecule and must be generated in situ. Here we show that pulsed-laser ablation of stable, non-toxic mixtures of Al with alkali or alkaline earth chlorides, denoted XCln, can provide a robust and reliable source of cold AlCl molecules. Both the chemical identity of XCln and the Al : XCln molar ratio are varied, and the yield of AlCl is monitored using absorption spectroscopy in a cryogenic gas. For KCl, the production of Al and K atoms was also monitored. We model the AlCl production in the limits of nonequilibrium recombination dominated by first-encounter events. The non-equilibrium model is in agreement with the data and also reproduces the observed trend with different XCln precursors. We find that AlCl production is limited by the solid-state densities of Al and Cl atoms and the recondensation of Al atoms in the ablation plume. We suggest future directions for optimizing the production of cold AlCl molecules using laser ablation. [ABSTRACT FROM AUTHOR]

Wedemonstrate the one-dimensional, transverse magneto-optical compression of a cold beam of calcium monofluoride (CaF). By continually alternating the magnetic field direction and laser polarizations of themagneto-optical trap (RFMOT), a photon scattering rate of 2π × 0.4 MHz is achieved. A 3Dmodel for this RF MOT, validated by agreement with data, predicts a 3DRFMOT capture velocity for CaF of 5ms-1. [ABSTRACT FROM AUTHOR]

Vibrational relaxation of strontium monohydroxide (SrOH) molecules in collisions with helium (He) at 2 K is studied.We find the diffusion cross section of SrOH at 2.2 K to be σ =±× − d (5 2) 10 cm 14 2 and the vibrational quenching cross sectionfor the (100) Sr–O stretching mode to be σq =±× − (7 2) 10 cm 17 2. The resulting ratio γ 100 = ∼ σ σ d q 700 is more than an order of magnitude smaller thanfor previously studiedfew-atom radicals (Au et al 2014 Phys. Rev.A90 032703 ).We also determine the Franck–Condonfactorfor SrOH ( Π Σ ← + A˜ (100) X˜ (000) 2 1 2 2 ) to be ± × − (4.8 0.8) 10 2., Physics

We demonstrate the mixing of rotational states in the ground electronic state using microwave radiation to enhance optical cycling in the molecule yttrium (II) monoxide (YO). This mixing technique is used in conjunction with a frequency modulated and chirped continuous wave laser to slow longitudinally a cryogenic buffer-gas beam of YO. We generate a flux of YO below, Physics

Direct loading of lanthanide atoms into magneto-optical traps (MOTs) from a very slow cryogenic buffer gas beam source is achieved, without the need for laser slowing. The beam source has an average forward velocity of 60– − 70ms 1 and a velocity half-width of ∼ − 35 m s 1 , which allows for direct MOT loading of Yb, Tm, Er and Ho. Residual helium background gas originating from the beam results in a maximum trap lifetime of about 80 ms (with Yb). The addition of a single-frequency slowing laser applied to the Yb in the buffer gas beam increases the number of trapped Yb atoms to 1.3 (0.7) 10 × 8 with a loading rate of × − 2.0 (1.0) 10 atoms s 10 1. Decay to metastable states is observed for all trapped species and decay rates are measured. Extension of this approach to the loading of molecules into a MOT is discussed., Physics

Calcium monofluoride (CaF) is magnetically slowed and trapped using optical pumping. Starting from a collisionally cooled slow beam, CaF with an initial velocity of ∼30 m/s is slowed via magnetic forces as it enters a 800 mK deep magnetic trap. Employing two-stage optical pumping, CaF is irreversibly loaded into the trap via two scattered photons. We observe a trap lifetime exceeding 500 ms limited by background collisions. This method paves the way for cooling and magnetic trapping of chemically diverse molecules without closed cycling transitions. [ABSTRACT FROM AUTHOR]

We demonstrate the preparation and coherent control of the angular momentum state of a two-ion crystal. The ions are prepared with an average angular momentum of 7850ℏ freely rotating at 100 kHz in a circularly symmetric potential, allowing us to address rotational sidebands. By coherently exciting these motional sidebands, we create superpositions of states separated by up to four angular momentum quanta. Ramsey experiments show the expected dephasing of the superposition which is dependent on the number of quanta separating the states. These results demonstrate coherent control of a collective motional state described as a quantum rotor in trapped ions. Moreover, our Letter offers an expansion of the utility of trapped ions for quantum simulation, interferometry, and sensing. [ABSTRACT FROM AUTHOR]

We demonstrate significantly improved magneto-optical trapping of molecules using a very slow cryogenic beam source and either rf modulated or dc magnetic fields. The rf magneto-optical trap (MOT) confines 1.0(3)×105 CaF molecules at a density of 7(3)×106 cm-3, which is an order of magnitude greater than previous molecular MOTs. Near Doppler-limited temperatures of 340(20) μK are attained. The achieved density enables future work to directly load optical tweezers and create optical arrays for quantum simulation. [ABSTRACT FROM AUTHOR]

We crystallize up to 15 40Ca+ ions in a ring with a microfabricated silicon surface Paul trap. Delocalization of the Doppler laser-cooled ions shows that the translational symmetry of the ion ring is preserved at millikelvin temperatures. By characterizing the collective motion of the ion crystals, we identify homogeneous electric fields as the dominant symmetry-breaking mechanism at this energy scale. With increasing ion numbers, such detrimental effects are reduced. We predict that, with only a ten-ion ring, uncompensated homogeneous fields will not break the translational symmetry of the rotational ground state. This experiment opens a door towards studying quantum many-body physics with translational symmetry at the single-particle level. [ABSTRACT FROM AUTHOR]