There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

Feshbach resonances are the essential tool to control the interaction between atoms in ultracold quantum gases. They have found numerous experimental applications, opening up the way to important breakthroughs. This review broadly covers the phenomenon of Feshbach resonances in ultracold gases and their main applications. This includes the theoretical background and models for the description of Feshbach resonances, the experimental methods to find and characterize the resonances, a discussion of the main properties of resonances in various atomic species and mixed atomic species systems, and an overview of key experiments with atomic Bose-Einstein condensates, degenerate Fermi gases, and ultracold molecules.

Feshbach resonances in ultracold gases

日本物理学会誌及びJournal of the Physical Society of Japanの月刊について

Recent advances1,2,3,4,5 in the magnetic trapping and evaporative cooling of atoms to nanokelvin temperatures have opened important areas of research, such as Bose–Einstein condensation and ultracold atomic collisions. Similarly, the ability to trap and cool molecules should facilitate the study of ultracold molecular physics and collisions6; improvements in molecular spectroscopy could be anticipated. Also, ultracold molecules could aid the search for electric dipole moments of elementary particles7. But although laser cooling (in the case of alkali metals1,8,9) and cryogenic surface thermalization (in the case of hydrogen10,11) are currently used to cool some atoms sufficiently to permit their loading into magnetic traps, such techniques are not applicable to molecules, because of the latter's complex internal energy-level structure. (Indeed, most atoms have resisted trapping by these techniques.) We have reported a more general loading technique12 based on elastic collisions with a cold buffer gas, and have used it to trap atomic chromium and europium13,14. Here we apply this technique to magnetically trap a molecular species—calcium monohydride (CaH). We use Zeeman spectroscopy to determine the number of trapped molecules and their temperature, and set upper bounds on the cross-sectional areas of collisional relaxation processes. The technique should be applicable to many paramagnetic molecules and atoms.

Magnetic trapping of calcium monohydride molecules at millikelvin temperatures

We describe planar and mostly planar current geometries for constructing microscopic magnetic traps for neutral atoms. These geometries are well-suited for fabrication from superconductors using standard microfabrication techniques. Magnetic-field gradients greater than 5×10^5 G/cm, and field curvatures greater than 10^8 G/cm^2 can be produced in microscopic traps. Trap loading could be accomplished by constructing a nested series of traps, and compressing atom clouds from larger traps into smaller ones. In the smallest magnetic microtraps the motional ground-state energy of atoms in the trap can exceed the recoil energy from resonant photons, which may allow direct laser cooling to the trap ground state. If a number of atoms can be simultaneously cooled to the ground state, the resulting "Bose clusters" should exhibit interesting optical behavior, since their spatial extent would be less than the resonant light wavelength.

/pdf/microscopic-magnetic-traps-for-neutral-atoms-48y8c5zbgl.pdf

Microscopic magnetic traps for neutral atoms

Over the past three years we have developed the technique of buer-gas cooling and loading of atoms and molecules into magnetic traps. Buer-gas cooling relies solely on elastic collisions (thermal- ization) of the species-to-be-trapped with a cryogenically cooled helium gas and so is independent of any particular energy level pattern. This makes the cooling technique general and potentially applicable to any species trappable at the temperature of the buer gas (as low as 240 mK). Using buer-gas loading, paramagnetic atoms (europium and chromium) as well as a molecule (calcium monohydride) were trapped at temperatures around 300 mK. The numbers of the trapped atoms and molecules were respectively about 10 12 and 10 8 . The atoms and molecules were produced by laser ablation of suitable solid precursors. In conjunction with evaporative cooling, buer-gas loaded magnetic traps oer the means to further lower the temperature and increase the density of the trapped ensemble to study a large variety of both static (spectra) and dynamic (collisional cross-sections) properties of many atoms and molecules at ultra-low tem- peratures. In this article we survey our main results obtained on Cr, Eu, and CaH and outline prospects for future work.

Buffer-gas loaded magnetic traps for atoms and molecules: A primer

Atomic europium has been magnetically trapped using buffer-gas loading. Laser ablated $\mathrm{Eu}(^{8}S_{7/2})$ atoms are thermalized to 800 mK in a ${}^{4}\mathrm{He}$ buffer gas (to 250 mK in a ${}^{3}\mathrm{He}$ buffer gas). Anti-Helmholtz superconducting coils produce a quadrupole magnetic field to trap the ${M}_{J}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}7/2$ state of Eu. Detection is via absorption spectroscopy at 462.7 nm. Up to $1\ifmmode\times\else\texttimes\fi{}{10}^{12}\mathrm{Eu}$ atoms are loaded at a central density of $5\ifmmode\times\else\texttimes\fi{}{10}^{12}\phantom{\rule{0ex}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. Atoms can be held for longer than 100 s.

/pdf/buffer-gas-loading-and-magnetic-trapping-of-atomic-europium-2l4palvkws.pdf

Buffer-Gas Loading and Magnetic Trapping of Atomic Europium

We demonstrate production of cold lead monoxide (PbO) molecules by laser ablation in a cryogenic cell filled with helium buffer gas and cooled by a cryostat to a temperature of 4 K. The molecules are probed by laser-induced fluorescence excited in the $\stackrel{\ensuremath{\rightarrow}}{X}B$ band. The molecules thermalize with the buffer gas, both translationally and rotationally, in less than 30 ms after the ablation pulse. A single ablation pulse fired at the solid PbO sample yields about ${10}^{12}$ cold molecules. We present an analysis indicating that buffer-gas cooled PbO molecules excited to either the a or B state could be effectively used to search for the permanent electric dipole moment of the electron.

Jonathan D. Weinstein

Papers

Magnetic trapping of calcium monohydride molecules at millikelvin temperatures

Microscopic magnetic traps for neutral atoms

Buffer-gas loaded magnetic traps for atoms and molecules: A primer

Buffer-Gas Loading and Magnetic Trapping of Atomic Europium

Spectroscopy of laser-ablated buffer-gas-cooled PbO at 4 K and the prospects for measuring the electric dipole moment of the electron