Session H2: Invited Session: Cold and Ultracold Molecules

Towards charge transfer or Sisyphus cooling of molecules (using ro-vibrational cooling)

Simple pulse shaping techniques of laser diodes has allowed us to manipulate, on demand, the rotational and vibrational population of di-atomic molecules. We have first demonstrated this optical pumping method on Cs2 [1]. Its extention to molecular beam will be discussed with BaF as an example. This paves the way to the production of brighter molecular beam as well as a possible new method of deceleration and production of cold molecular cloud. We will detail and present ideas based on charge transfer and Sisyphus cooling with results on BaF. \\[4pt] [1] Rovibrational Cooling of Molecules by Optical Pumping I. Manai, R. Horchani, H. Lignier, P. Pillet, D. Comparat, A. Fioretti, M. Allegrini, Phys. Rev. Lett. 109, 183001 (2012)   

Precision measurements with an ultracold molecular clock

High-precision spectroscopy has been instrumental in the progress of atomic physics. In this talk, we extend precision spectroscopy techniques to ultracold diatomic strontium molecules tightly trapped in an optical lattice, and discuss the results from the point of view of molecular and fundamental science. For weakly bound molecules near the atomic threshold corresponding to the narrow intercombination transition, we observe peculiar and unexpected physics, including multiply forbidden transitions and anomalously large linear and quadratic Zeeman shifts. The Zeeman shifts are highly sensitive to nonadiabatic mixing angles of the molecular wave functions. For the first time, we quantitatively compare the electric- and magnetic-dipole transition strengths for forbidden transitions in molecules, and discuss the dependence on the internuclear separation. In addition, we study ground state molecules, and discuss the present status of the molecular lattice clock and the physics it is able to probe. Magic-wavelength spectroscopy is successfully demonstrated for a range of narrow molecular transitions.   

Detection of chiral molecules

Recent years have seen an enormous growth of rich physics performed with cold samples of diatomic molecules, as well as impressive demonstrations of techniques to cool polyatomic molecules containing several ($\sim$7) atoms. Here we present progress in our methods to produce cold, dense, slow moving samples of molecules of many ($>$20) atoms from cryogenic buffer gas cells. The ability to produce cold, slow samples of such molecules opens up a host of potential research paths, including ultra-high precision spectroscopy, searches for changes in fundamental constants, and a rich set of experiments in the complex, low-decoherence Hilbert space spanned by the rotational and hyperfine states of such molecules. As an early demonstration of the rich physics offered in such systems, recent results demonstrating chirality-sensitive microwave spectroscopy of cold molecules will be presented.   

Generating ensembles of polyatomic molecules at cold and ultracold temperatures

Realizing a source of molecules at cold and ultracold temperatures is a formidable challenge. To this end, our group is following a multipronged approach. As an initial source of molecules, velocity filtering~[1] and buffergas cooling~[2] can be used. To reduce the velocity of fast molecules from these sources to trappable speeds, we have recently demonstrated a novel centrifuge decelerator~[3]. A key feature of this deceleration technique is its ability to decelerate continuous beams. Once the molecules are trapped, we have demonstrated optoelectrical Sisyphus cooling~[4] to further reduce the temperature. Our current efforts, focused on combining the various approaches and further reducing the temperature to the submillikelvin regime, will be discussed.\\[4pt] [1] S.A. Rangwala et al., Phys. Rev. A {\bf 67}, 043406 (2003)\\[0pt] [2] L.D. van Buuren et al., Phys. Rev. Lett. {\bf 102}, 033001 (2009)\\[0pt] [3] S. Chervenkov et al., Phys. Rev. Lett. {\bf 112}, 013001 (2014)\\[0pt] [4] M. Zeppenfeld et al., Nature {\bf 491}, 570 (2012)