2,820 research outputs found
Multipolar theory of black-body radiation shift of atomic energy levels and its implications for optical lattice clocks
A black-body radiation (BBR) shifts of (nsnp ^3P_0) - (ns^2 ^1S_0) clock
transition in divalent atoms Mg, Ca, Sr, and Yb are evaluated. A theory of
multipolar BBR shifts is developed and its implications are discussed. At room
temperatures, the resulting uncertainties in the BBR shifts are relatively
large and substantially affect the projected 10^{-18} fractional accuracy of
the optical-lattice-based clocks.Comment: 4 pages, 1 figure, submitted to Physical Review Letter
Morphology of the Acromion and Scapular Spine with Special Interest in the Strength & Failure Prediction after Reverse Total Shoulder Replacement
Scapular spine fractures following a reverse arthroplasty are a significant clinical concern. This ongoing study looks at the morphology of the acromion and scapular spine with an interest in the strength and failure prediction of the bone. Digital 3D models of the scapular spine were created from cadaver CTs, then bone density and distribution data was obtained. It was found that the cortical bone was most dense just medial of the lateral angle. The cross-sectional area here was also the largest and decreased medially. This has important implications for implant fixation hardware as cortical bone --compared to cancellous bone-- is stronger, denser, and therefore a better option for fixation hardware
Relativistic coupled-cluster single-double method applied to alkali-metal atoms
A relativistic version of the coupled-cluster single-double (CCSD) method is
developed for atoms with a single valence electron. In earlier work, a
linearized version of the CCSD method (with extensions to include a dominant
class of triple excitations) led to accurate predictions for energies,
transition amplitudes, hyperfine constants, and other properties of monovalent
atoms. Further progress in high-precision atomic structure calculations for
heavy atoms calls for improvement of the linearized coupled-cluster
methodology. In the present work, equations for the single and double
excitation coefficients of the Dirac-Fock wave function, including all
non-linear coupled-cluster terms that contribute at the single-double level are
worked out. Contributions of the non-linear terms to energies, electric-dipole
matrix elements, and hyperfine constants of low-lying states in alkali-metal
atoms from Li to Cs are evaluated and the results are compared with other
calculations and with precise experiments.Comment: 12 page
Piano Studio Recital, September 24, 2019
Carter Campbell, from the studio of Professor Kasparov
Andrei S. Johnson, from the studio of Professor Lutsyshyn
Joel Sanford, from the studio of Professor Toomey
Robert Stahl, from the studio of Professor Rayd
Piano Studio Recital, October 22, 2019
Carter Campbell, from the studio of Professor Kasparov
Andrei S Johnson, from the studio of Professor Lutsyshyn
Joel Sanford, from the studio of Professor Toomey
Robert Stahl, from the studio of Professor Rayd
Towards a gauge invariant volume-weighted probability measure for eternal inflation
An improved volume-weighted probability measure for eternal inflation is
proposed. For the models studied in this paper it leads to simple and
intuitively expected gauge-invariant results.Comment: 16 pages, 3 figs, few misprints corrected, comments adde
Optical Multi-Gas Monitor Technology Demonstration on the International Space Station
The International Space Station (ISS) employs a suite of portable and permanently located gas monitors to insure crew health and safety. These sensors are tasked with functions ranging from fixed mass spectrometer based major constituents analysis to portable electrochemical sensor based combustion product monitoring. An all optical multigas sensor is being developed that can provide the specificity of a mass spectrometer with the portability of an electrochemical cell. The technology, developed under the Small Business Innovation Research program, allows for an architecture that is rugged, compact and low power. A four gas version called the Multi-Gas Monitor was launched to ISS in November 2013 aboard Soyuz and activated in February 2014. The portable instrument is comprised of a major constituents analyzer (water vapor, carbon dioxide, oxygen) and high dynamic range real-time ammonia sensor. All species are sensed inside the same enhanced path length optical cell with a separate vertical cavity surface emitting laser (VCSEL) targeted at each species. The prototype is controlled digitally with a field-programmable gate array/microcontroller architecture. The optical and electronic approaches are designed for scalability and future versions could add three important acid gases and carbon monoxide combustion product gases to the four species already sensed. Results obtained to date from the technology demonstration on ISS are presented and discussed
Correlated many-body treatment of Breit interaction with application to cesium atomic properties and parity violation
Corrections from Breit interaction to basic properties of atomic 133Cs are
determined in the framework of third-order relativistic many-body perturbation
theory. The corrections to energies, hyperfine-structure constants,
off-diagonal hyperfine 6S-7S amplitude, and electric-dipole matrix elements are
tabulated. It is demonstrated that the Breit corrections to correlations are
comparable to the Breit corrections at the Dirac-Hartree-Fock level.
Modification of the parity-nonconserving (PNC) 6S-7S amplitude due to Breit
interaction is also evaluated; the resulting weak charge of Cs shows no
significant deviation from the prediction of the standard model of elementary
particles. The neutron skin correction to the PNC amplitude is also estimated
to be -0.2% with an error bound of 30% based on the analysis of recent
experiments with antiprotonic atoms. The present work supplements publication
[A. Derevianko, Phys. Rev. Lett. 85, 1618 (2000)] with a discussion of the
formalism and provides additional numerical results and updated discussion of
parity violation.Comment: 16 pages; 5 figs; submitted to Phys. Rev.
High-accuracy relativistic many-body calculations of van der Waals coefficients C_6 for alkaline-earth atoms
Relativistic many-body calculations of van der Waals coefficients C_6 for
dimers correlating to two ground state alkaline-earth atoms at large
internuclear separations are reported. The following values and uncertainties
were determined : C_6 = 214(3) for Be, 627(12) for Mg, 2221(15) for Ca,
3170(196) for Sr, and 5160(74) for Ba in atomic units.Comment: 5 pages, submitted to Phys. Rev.
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