Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Researchers cooled trapped molecules well below 1 mK---a record temperature for molecules that have not been assembled from pre-cooled atoms.

/pdf/submillikelvin-dipolar-molecules-in-a-radio-frequency-3ht1s6nd2u.pdf

Submillikelvin dipolar molecules in a radio-frequency magneto-optical trap

Permanent electric dipole moments are important for understanding symmetry breaking in molecular physics, control of chemical reactions, and realization of strongly correlated many-body quantum systems. However, large molecular permanent electric dipole moments are challenging to realize experimentally. We report the observation of ultralong-range Rydberg molecules with bond lengths of ~100 nanometers and kilo-Debye permanent electric dipole moments that form when an ultracold ground-state cesium (Cs) atom becomes bound within the electronic cloud of an extended Cs electronic orbit. The electronic character of this hybrid class of “trilobite” molecules is dominated by degenerate Rydberg manifolds, making them difficult to produce by conventional photoassociation. We used detailed coupled-channel calculations to reproduce their properties quantitatively. Our findings may lead to progress in ultracold chemistry and strongly correlated many-body physics.

http://science.sciencemag.org/content/sci/348/6230/99.full.pdf

Production of trilobite Rydberg molecule dimers with kilo-Debye permanent electric dipole moments

Ultracold Rydberg atoms — atoms with highly excited electrons — can form molecules with ground state atoms. By tuning the principal quantum number of the Rydberg state, Gaj et al. study the transition from resolvable molecular lines to the mean shift regime, where indistinguishable lines form a band.

/pdf/from-molecular-spectra-to-a-density-shift-in-dense-rydberg-4l76551mlb.pdf

From molecular spectra to a density shift in dense Rydberg gases.

We demonstrate the efficient transfer of molecules from a magneto-optical trap into a conservative magnetic quadrupole trap. Our scheme begins with a blue-detuned optical molasses to cool SrF molecules to $\ensuremath{\approx}50\text{ }\text{ }\ensuremath{\mu}\mathrm{K}$. Next, we optically pump the molecules into a strongly trapped sublevel. This two-step process reliably transfers $\ensuremath{\approx}40%$ of the molecules initially trapped in the magneto-optical trap into a single quantum state in the magnetic trap. Once loaded, the molecule cloud is compressed by increasing the magnetic field gradient. We observe a magnetic trap lifetime of over 1 s. This opens a promising new path to study ultracold molecular collisions, and potentially to produce quantum-degenerate molecular gases via sympathetic cooling with co-trapped atoms.

Magnetic Trapping of an Ultracold Gas of Polar Molecules.

We observe "trilobitelike" states of ultracold (85)Rb(2) molecules, in which a ground-state atom is bound by the electronic wave function of its Rydberg-atom partner. We populate these states through the ultraviolet excitation of weakly bound molecules, and access a regime of trilobitelike states at low principal quantum numbers and with vibrational turning points around 35 Bohr radii. This demonstrates that, unlike previous studies that used free-to-bound transitions, trilobitelike states can also be excited through bound-to-bound transitions. This approach provides high excitation probabilities without requiring high-density samples, and affords the ability to control the excitation radius by selection of the initial-state vibrational level.

Excitation of weakly bound molecules to trilobitelike Rydberg states.

We report the production of ultracold RbCs molecules in the rovibronic ground state, ie, $X{\phantom{\rule{016em}{0ex}}}^{1}{\ensuremath{\Sigma}}^{+}(v=0,J=0)$, by short-range photoassociation to the $2{\phantom{\rule{016em}{0ex}}}^{3}{\ensuremath{\Pi}}_{0}$ state followed by spontaneous emission We use narrow-band depletion spectroscopy to probe the distribution of rotational levels formed in the $X{\phantom{\rule{016em}{0ex}}}^{1}{\ensuremath{\Sigma}}^{+}(v=0)$ state We conclude, based on selection rules, that the primary decay route to $X{\phantom{\rule{016em}{0ex}}}^{1}{\ensuremath{\Sigma}}^{+}(v=0)$ is a two-step cascade decay that leads to as much as $33%$ branching into the $J=0$ rotational level The experimental simplicity of our scheme opens up the possibility of easier access to the study and manipulation of ultracold heteronuclear molecules in the rovibronic ground state

https://link.aps.org/accepted/10.1103/PhysRevA.91.021401

Production of rovibronic-ground-state RbCs molecules via two-photon-cascade decay

We report continuous direct photoassociative formation of ultracold KRb molecules in the lowest vibrational levels $({v}^{\ensuremath{'}\ensuremath{'}}=0\ensuremath{-}10)$ of the electronic ground state $(X{\phantom{\rule{0.16em}{0ex}}}^{1}{\ensuremath{\Sigma}}^{+})$, starting from ${}^{39}$K and ${}^{85}$Rb atoms in a magneto-optical trap. The process exploits a new-found resonant coupling between the $2(1),\phantom{\rule{0.16em}{0ex}}{v}^{\ensuremath{'}}=165$ and $4(1),\phantom{\rule{0.16em}{0ex}}{v}^{\ensuremath{'}}=61$ levels, which exhibit an almost equal admixture of the uncoupled eigenstates. The production rate of the ${X}^{1}{\ensuremath{\Sigma}}^{+}$ $({v}^{\ensuremath{'}\ensuremath{'}}=0)$ level is estimated to be $5\ifmmode\times\else\texttimes\fi{}{10}^{3}$ molecules/s.

Direct photoassociative formation of ultracold KRb molecules in the lowest vibrational levels of the electronic ground state

Promising pathways for photoassociative formation of ultracold heteronuclear alkali metal dimers in their lowest rovibronic levels (denoted X(0,0)) are examined using high-quality ab initio calculations of potential energy curves currently available. A promising pathway for KRb, involving the resonant coupling of the 21Π and 11Π states just below the lowest excited asymptote (K(4s) + Rb(5p1/2)), is found to occur also for RbCs and less promisingly for KCs also. The resonant coupling of the 31Σ+ and 11Π states, also just below the lowest excited asymptote, is found to be promising for LiNa, LiK, and LiRb and less promising for LiCs and KCs. Direct photoassociation to the 11Π state near dissociation appears promising in the final dimers NaK, NaRb, and NaCs, although detuning more than 100 cm−1 below the lowest excited asymptote may be required.

Resonant coupling in the heteronuclear alkali dimers for direct photoassociative formation of X(0,0) ultracold molecules.

We report on the observation of blue-detuned photoassociation in Rb(2), in which vibrational levels are energetically above the corresponding excited atomic asymptote. (85)Rb atoms in a MOT were photoassociated at short internuclear distance to levels of the 1(3)Π(g) state at a rate of approximately 5 × 10(4) molecules s(-1). We have observed most of the predicted vibrational levels for all four spin-orbit components; 0(+)(g), 0(-)(g), 1(g), and 2(g), including levels of the 0(+)(g) outer well. These molecules decay to the metastable a(3)Σ(+)(u) state, some preferentially to the v'' = 0 level, as we have observed for photoassociation to the v' = 8 level of the 1(g) component.

Michael Bellos

Papers

Excitation of weakly bound molecules to trilobitelike Rydberg states.

Production of rovibronic-ground-state RbCs molecules via two-photon-cascade decay

Direct photoassociative formation of ultracold KRb molecules in the lowest vibrational levels of the electronic ground state

Resonant coupling in the heteronuclear alkali dimers for direct photoassociative formation of X(0,0) ultracold molecules.

Formation of ultracold Rb2 molecules in the v′′ = 0 level of the a3Σ+u state via blue-detuned photoassociation to the 13Πg state