27,999 research outputs found
Photoassociation adiabatic passage of ultracold Rb atoms to form ultracold Rb_2 molecules
We theoretically explore photoassociation by Adiabatic Passage of two
colliding cold ^{85}Rb atoms in an atomic trap to form an ultracold Rb_2
molecule. We consider the incoherent thermal nature of the scattering process
in a trap and show that coherent manipulations of the atomic ensemble, such as
adiabatic passage, are feasible if performed within the coherence time window
dictated by the temperature, which is relatively long for cold atoms. We show
that a sequence of ~2*10^7 pulses of moderate intensities, each lasting ~750
ns, can photoassociate a large fraction of the atomic ensemble at temperature
of 100 microkelvin and density of 10^{11} atoms/cm^3. Use of multiple pulse
sequences makes it possible to populate the ground vibrational state. Employing
spontaneous decay from a selected excited state, one can accumulate the
molecules in a narrow distribution of vibrational states in the ground
electronic potential. Alternatively, by removing the created molecules from the
beam path between pulse sets, one can create a low-density ensemble of
molecules in their ground ro-vibrational state.Comment: RevTex, 23 pages, 9 figure
Judicial Incentives and Indeterminacy in Substantive Review of Administrative Decisions
Uppsatsen tydliggör och beskriver innehållet i elva lokala överenskommelser (LÖK) mellan civilsamhället och offentlig sektor. Studien visar också hur relationen mellan parterna avspeglas i texterna. Uppsatsen visar också på hur olika idéer och synsätt i överenskommelserna kan få praktiska konsekvenser för civilsamhället
Judicial Incentives and Indeterminacy in Substantive Review of Administrative Decisions
In the Chevron and State Farm cases the Supreme Court announced what appeared to be controlling standards for substantive review of administrative decisions. Instead, the Chevron framework has broken down, and State Farm has been all but ignored by agencies and the courts, including the Supreme Court. This article accounts for this breakdown by analyzing the impact of judicial incentives on substantive review in administrative law
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The Enlightenment of Administrative Law: Looking Inside the Agency for Legitimacy
This article’s investigation into the “agency for legitimacy” proceeds in five steps: Part I introduces the concept of “administrative constitutionalism,” which encompasses the debate over what should be the role and nature of public administration to ensure its legitimacy. It then lays out the elements of the rational-instrumental and deliberative-constitutive paradigms and explains how they contribute to administrative constitutionalism respectively from the outside-in and inside-out. Part II provides a brief history of administrative constitutionalism, which reveals there have been ongoing tensions between two paradigms—and thus between outside in and inside out accountability—since the 1880s. Part III elaborates on the authors’ argument that the current emphasis on the rational-instrumental model has been administrative constitutionalism unsustainable. Part IV argues that acknowledging and developing the deliberative-constitutive paradigm will strengthen administrative constitutionalism by admitting the existence of agency discretion and by looking for realistic ways to make it accountable. Finally, Part V offers a case study in how the deliberative-constitutive paradigm can contribute to administrative constitutionalism.The Kay Bailey Hutchison Center for Energy, Law, and Busines
Pulsed Adiabatic Photoassociation via Scattering Resonances
We develop the theory for the Adiabatic Raman Photoassociation (ARPA) of
ultracold atoms to form ultracold molecules in the presence of scattering
resonances. Based on a computational method in which we replace the continuum
with a discrete set of "effective modes", we show that the existence of
resonances greatly aids in the formation of deeply bound molecular states. We
illustrate our general theory by computationally studying the formation of
Rb molecules from pairs of colliding ultracold Rb atoms. The
single-event transfer yield is shown to have a near-unity value for wide
resonances, while the ensemble-averaged transfer yield is shown to be higher
for narrow resonances. The ARPA yields are compared with that of (the
experimentally measured) "Feshbach molecule" magneto-association. Our findings
suggest that an experimental investigation of ARPA at sub-K temperatures
is warranted.Comment: 20 pages, 11 figure
Nonlinearity and pixel shifting effects in HXRG infrared detectors
We study the nonlinearity (NL) in the conversion from charge to voltage in
infrared detectors (HXRG) for use in precision astronomy. We present laboratory
measurements of the NL function of a H2RG detector and discuss the accuracy to
which it would need to be calibrated in future space missions to perform
cosmological measurements through the weak gravitational lensing technique. In
addition, we present an analysis of archival data from the infrared H1RG
detector of the Wide Field Camera 3 in the Hubble Space Telescope that provides
evidence consistent with the existence of a sensor effect analogous to the
brighter-fatter effect found in Charge-Coupled Devices. We propose a model in
which this effect could be understood as shifts in the effective pixel
boundaries, and discuss prospects of laboratory measurements to fully
characterize this effect.Comment: Accepted for publication in the Journal of Instrumentation (JINST).
Part of "Precision Astronomy with Fully Depleted CCDs" (Dec 1-2, 2016),
Brookhaven National Laboratory, Upton, NY, US
The place of the Sun among the Sun-like stars
Context. Monitoring of the photometric and chromospheric HK emission data
series of stars similar to the Sun in age and average activity level showed
that there is an empirical correlation between the average stellar
chromospheric activity level and the photometric variability. In general, more
active stars show larger photometric variability. Interestingly, the
measurements and reconstructions of the solar irradiance show that the Sun is
significantly less variable than indicated by the empirical relationship. Aims.
We aim to identify possible reasons for the Sun to be currently outside of this
relationship. Methods. We employed different scenarios of solar HK emission and
irradiance variability and compared them with available time series of Sun-like
stars. Results. We show that the position of the Sun on the diagram of
photometric variability versus chromospheric activity changes with time. The
present solar position is different from its temporal mean position as the
satellite era of continuous solar irradiance measurements has accidentally
coincided with a period of unusually high and stable solar activity. Our
analysis suggests that although present solar variability is significantly
smaller than indicated by the stellar data, the temporal mean solar variability
might be in agreement with the stellar data. We propose that the continuation
of the photometric program and its expansion to a larger stellar sample will
ultimately allow us to constrain the historical solar variability.Comment: 10 pages, 5 figures, accepted for publication in
Astronomy&Astrophysic
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