8 research outputs found
Formation of ultracold RbCs molecules by photoassociation
The formation of ultracold metastable RbCs molecules is observed in a double
species magneto-optical trap through photoassociation below the
^85Rb(5S_1/2)+^133Cs(6P_3/2) dissociation limit followed by spontaneous
emission. The molecules are detected by resonance enhanced two-photon
ionization. Using accurate quantum chemistry calculations of the potential
energy curves and transition dipole moment, we interpret the observed
photoassociation process as occurring at short internuclear distance, in
contrast with most previous cold atom photoassociation studies. The vibrational
levels excited by photoassociation belong to the 5th 0^+ or the 4th 0^-
electronic states correlated to the Rb(5P_1/2,3/2)+Cs(6S_1/2) dissociation
limit. The computed vibrational distribution of the produced molecules shows
that they are stabilized in deeply bound vibrational states of the lowest
triplet state. We also predict that a noticeable fraction of molecules is
produced in the lowest level of the electronic ground state
Dark resonances for ground state transfer of molecular quantum gases
One possible way to produce ultracold, high-phase-space-density quantum gases
of molecules in the rovibronic ground state is given by molecule association
from quantum-degenerate atomic gases on a Feshbach resonance and subsequent
coherent optical multi-photon transfer into the rovibronic ground state. In
ultracold samples of Cs_2 molecules, we observe two-photon dark resonances that
connect the intermediate rovibrational level |v=73,J=2> with the rovibrational
ground state |v=0,J=0> of the singlet ground state potential.
For precise dark resonance spectroscopy we exploit the fact that it is possible
to efficiently populate the level |v=73,J=2> by two-photon transfer from the
dissociation threshold with the stimulated Raman adiabatic passage (STIRAP)
technique. We find that at least one of the two-photon resonances is
sufficiently strong to allow future implementation of coherent STIRAP transfer
of a molecular quantum gas to the rovibrational ground state |v=0,J=0>.Comment: 7 pages, 4 figure
Hydrogen-like nitrogen radio line from hot interstellar and warm-hot intergalactic gas
Hyperfine structure lines of highly-charged ions may open a new window in
observations of hot rarefied astrophysical plasmas. In this paper we discuss
spectral lines of isotopes and ions abundant at temperatures 10^5-10^7 K,
characteristic for warm-hot intergalactic medium, hot interstellar medium,
starburst galaxies, their superwinds and young supernova remnants. Observations
of these lines will allow to study bulk and turbulent motions of the observed
target and will broaden the information about the gas ionization state,
chemical and isotopic composition.
The most prospective is the line of the major nitrogen isotope having
wavelength 5.65 mm (Sunyaev and Churazov 1084). Wavelength of this line is
well-suited for observation of objects at z=0.15-0.6 when it is redshifted to
6.5-9 mm spectral band widely-used in ground-based radio observations, and, for
example, for z>=1.3, when the line can be observed in 1.3 cm band and at lower
frequencies. Modern and future radio telescopes and interferometers are able to
observe the absorption by 14-N VII in the warm-hot intergalactic medium at
redshifts above z=0.15 in spectra of brightest mm-band sources. Sub-millimeter
emission lines of several most abundant isotopes having hyperfine splitting
might also be detected in spectra of young supernova remnants.Comment: 12 pages, 5 figures, accepted by Astronomy Letters; v3: details
added; error fixe
Formation and interactions of cold and ultracold molecules: new challenges for interdisciplinary physics
Progress on researches in the field of molecules at cold and ultracold
temperatures is reported in this review. It covers extensively the experimental
methods to produce, detect and characterize cold and ultracold molecules
including association of ultracold atoms, deceleration by external fields and
kinematic cooling. Confinement of molecules in different kinds of traps is also
discussed. The basic theoretical issues related to the knowledge of the
molecular structure, the atom-molecule and molecule-molecule mutual
interactions, and to their possible manipulation and control with external
fields, are reviewed. A short discussion on the broad area of applications
completes the review.Comment: to appear in Reports on Progress in Physic
Athlome Project Consortium: a concerted effort to discover genomic and other "omic" markers of athletic performance.
Despite numerous attempts to discover genetic variants associated with elite athletic performance, injury predisposition, and elite/world-class athletic status, there has been limited progress to date. Past reliance on candidate gene studies predominantly focusing on genotyping a limited number of single nucleotide polymorphisms or the insertion/deletion variants in small, often heterogeneous cohorts (i.e., made up of athletes of quite different sport specialties) have not generated the kind of results that could offer solid opportunities to bridge the gap between basic research in exercise sciences and deliverables in biomedicine. A retrospective view of genetic association studies with complex disease traits indicates that transition to hypothesis-free genome-wide approaches will be more fruitful. In studies of complex disease, it is well recognized that the magnitude of genetic association is often smaller than initially anticipated, and, as such, large sample sizes are required to identify the gene effects robustly. A symposium was held in Athens and on the Greek island of Santorini from 14-17 May 2015 to review the main findings in exercise genetics and genomics and to explore promising trends and possibilities. The symposium also offered a forum for the development of a position stand (the Santorini Declaration). Among the participants, many were involved in ongoing collaborative studies (e.g., ELITE, GAMES, Gene SMART, GENESIS, and POWERGENE). A consensus emerged among participants that it would be advantageous to bring together all current studies and those recently launched into one new large collaborative initiative, which was subsequently named the Athlome Project Consortium
Dust in Supernovae and Supernova Remnants II: Processing and survival
Observations have recently shown that supernovae are efficient dust factories, as predicted for a long time by theoretical models. The rapid evolution of their stellar progenitors combined with their efficiency in precipitating refractory elements from the gas phase into dust grains make supernovae the major potential suppliers of dust in the early Universe, where more conventional sources like Asymptotic Giant Branch (AGB) stars did not have time to evolve. However, dust yields inferred from observations of young supernovae or derived from models do not reflect the net amount of supernova-condensed dust able to be expelled from the remnants and reach the interstellar medium. The cavity where the dust is formed and initially resides is crossed by the high velocity reverse shock which is generated by the pressure of the circumstellar material shocked by the expanding supernova blast wave. Depending on grain composition and initial size, processing by the reverse shock may lead to substantial dust erosion and even complete destruction. The goal of this review is to present the state of the art about processing and survival of dust inside supernova remnants, in terms of theoretical modelling and comparison to observations