7,813 research outputs found
Covariant spectator theory of np scattering: Effective range expansions and relativistic deuteron wave functions
We present the effective range expansions for the 1S_0 and 3S_1 scattering
phase shifts, and the relativistic deuteron wave functions that accompany our
recent high precision fits (with chi^2/N{data} approx 1) to the 2007 world np
data below 350 MeV. The wave functions are expanded in a series of analytical
functions (with the correct asymptotic behavior at both large and small
arguments) that can be Fourier-transformed from momentum to coordinate space
and are convenient to use in any application. A fortran subroutine to compute
these wave functions can be obtained from the authors.Comment: 32 pages, 14 figure
Parametric downconversion with optimized spectral properties in nonlinear photonic crystals
We study the joint spectral properties of photon pairs generated by
spontaneous parametric down-conversion in a one-dimensional nonlinear photonic
crystal in a collinear, degenerate, type-II geometry. We show that the photonic
crystal properties may be exploited to compensate for material dispersion and
obtain photon pairs that are nearly factorable, in principle, for arbitrary
materials and spectral regions, limited by the ability to fabricate the
nonlinear crystal with the required periodic variation in the refractive
indices for the ordinary and extraordinary waves.Comment: 9 pages, 6 figure
Digital cartography of Io
A high resolution controlled mosaic of the hemisphere of Io centered on longitude 310 degrees is produced. Digital cartographic techniques were employed. Approximately 80 Voyager 1 clear and blue filter frames were utilized. This mosaic was merged with low-resolution color images. This dataset is compared to the geologic map of this region. Passage of the Voyager spacecraft through the Io plasma torus during acquisition of the highest resolution images exposed the vidicon detectors to ionized radiation, resulting in dark-current buildup on the vidicon. Because the vidicon is scanned from top to bottom, more charge accumulated toward the bottom of the frames, and the additive error increases from top to bottom as a ramp function. This ramp function was removed by using a model. Photometric normalizations were applied using the Minnaert function. An attempt to use Hapke's photometric function revealed that this function does not adequately describe Io's limb darkening at emission angles greater than 80 degrees. In contrast, the Minnaert function accurately describes the limb darkening up to emission angles of about 89 degrees. The improved set of discrete camera angles derived from this effort will be used in conjunction with the space telemetry pointing history file (the IPPS file), corrected on 4 or 12 second intervals to derive a revised time history for the pointing of the Infrared Interferometric Spectrometer (IRIS). For IRIS observations acquired between camera shutterings, the IPPS file can be corrected by linear interpolation, provided that the spacecraft motions were continuous. Image areas corresponding to the fields of view of IRIS spectra acquired between camera shutterings will be extracted from the mosaic to place the IRIS observations and hotspot models into geologic context
Generation of Fourier transform limited heralded single photons
In this paper we study the spectral (temporal) properties of heralded single
photon wavepackets, triggered by the detection of an idler photon in the
process of parametric downconversion. The generated single photons are studied
within the framework of the chronocyclic Wigner function, from which the single
photon spectral width and temporal duration can be computed. We derive specific
conditions on the two-photon joint spectral amplitude which result in both pure
and Fourier- transform limited heralded single photons. Likewise, we present
specific source geometries which lead to the fulfilment of these conditions and
show that one of these geometries leads, for a given pump bandwidth, to the
temporally shortest possible heralded single photon wavepackets.Comment: 10 pages, 3 figure, PHYSICAL REVIEW A 75, 02381
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