49 research outputs found
Loading atoms from a large magnetic trap to a small intra-cavity dipole trap
We show that an optimized loading of a cold ensemble of rubidium-87 atoms
from a magnetic trap into an optical dipole trap sustained by a single,
far-red-detuned mode of a high-Q optical cavity can be efficient despite the
large volume mismatch of the traps. The magnetically trapped atoms are
magnetically transported to the vicinity of the cavity mode and released from
the magnetic trap in a controlled way meanwhile undergoing an evaporation
period. Large number of atoms get trapped in the dipole potential for several
hundreds of milliseconds. We monitor the number of atoms in the mode volume by
a second tone of the cavity close to the atomic resonance. While this probe
tone can pump atoms to another ground state uncoupled to the probe, we
demonstrate state-independent trapping by applying a repumper laser
Multimode mean-field model for the quantum phase transition of a Bose-Einstein condensate in an optical resonator
We develop a mean-field model describing the Hamiltonian interaction of
ultracold atoms and the optical field in a cavity. The Bose-Einstein condensate
is properly defined by means of a grand-canonical approach. The model is
efficient because only the relevant excitation modes are taken into account.
However, the model goes beyond the two-mode subspace necessary to describe the
self-organization quantum phase transition observed recently. We calculate all
the second-order correlations of the coupled atom field and radiation field
hybrid bosonic system, including the entanglement between the two types of
fields.Comment: 10 page
Advances in structure elucidation of small molecules using mass spectrometry
The structural elucidation of small molecules using mass spectrometry plays an important role in modern life sciences and bioanalytical approaches. This review covers different soft and hard ionization techniques and figures of merit for modern mass spectrometers, such as mass resolving power, mass accuracy, isotopic abundance accuracy, accurate mass multiple-stage MS(n) capability, as well as hybrid mass spectrometric and orthogonal chromatographic approaches. The latter part discusses mass spectral data handling strategies, which includes background and noise subtraction, adduct formation and detection, charge state determination, accurate mass measurements, elemental composition determinations, and complex data-dependent setups with ion maps and ion trees. The importance of mass spectral library search algorithms for tandem mass spectra and multiple-stage MS(n) mass spectra as well as mass spectral tree libraries that combine multiple-stage mass spectra are outlined. The successive chapter discusses mass spectral fragmentation pathways, biotransformation reactions and drug metabolism studies, the mass spectral simulation and generation of in silico mass spectra, expert systems for mass spectral interpretation, and the use of computational chemistry to explain gas-phase phenomena. A single chapter discusses data handling for hyphenated approaches including mass spectral deconvolution for clean mass spectra, cheminformatics approaches and structure retention relationships, and retention index predictions for gas and liquid chromatography. The last section reviews the current state of electronic data sharing of mass spectra and discusses the importance of software development for the advancement of structure elucidation of small molecules