4,270 research outputs found
High-Precision Optical Measurement of the 2S Hyperfine Interval in Atomic Hydrogen
We have applied an optical method to the measurement of the 2S hyperfine
interval in atomic hydrogen. The interval has been measured by means of
two-photon spectroscopy of the 1S-2S transition on a hydrogen atomic beam
shielded from external magnetic fields. The measured value of the 2S hyperfine
interval is equal to 177 556 860(15) Hz and represents the most precise
measurement of this interval to date. The theoretical evaluation of the
specific combination of 1S and 2S hyperfine intervals D_21 is in moderately
good agreement with the value for D_21 deduced from our measurement
Pilot cryo tunnel: Attachments, seals, and insulation
Several different tests are described which simulated the actual configuration of a cryogenic wind tunnel operating at pressures up to 5 atmospheres (507 kPa) and temperatures from -320 F (78K) to 120 F (322K) in order to determine compatible bolting, adequate sealing, and effective insulating materials. The evaluation of flange attachments (continuous threaded studs) considered bolting based on compatible flanges, attachment materials, and prescribed bolt elongations. Various types of seals and seal configurations were studied to determine suitability and reusability under the imposed pressure and temperature loadings. The temperature profile was established for several materials used for structural supports
Electroweak Beautygenesis: From b {\to} s CP-violation to the Cosmic Baryon Asymmetry
We address the possibility that CP-violation in mixing may
help explain the origin of the cosmic baryon asymmetry. We propose a new
baryogenesis mechanism - "Electroweak Beautygenesis" - explicitly showing that
these two CP-violating phenomena can be sourced by a common CP-phase. As an
illustration, we work in the Two-Higgs-Doublet model. Because the relevant
CP-phase is flavor off-diagonal, this mechanism is less severely constrained by
null results of electric dipole moment searches than other scenarios. We show
how measurements of flavor observables by the D0, CDF, and LHCb collaborations
test this scenario.Comment: 4 pages, 1 figure, 1 tabl
Results of an investigation of the 0.003-scale space shuttle external tank MSFC model 460 in the NASA/MSFC 14 x 14 inch Trisonic Wind Tunnel to determine static pressure distributions during reentry (TA2F), volume 3
Static pressure distributions for the external tank (ET) at reentry conditions are presented. Basic configuration of the model was the MCR 0200 ET modified to include a rectangular crossbar at the aft ET/orbiter attach point. Mach numbers were 1.96, 3.48, and 4.96. Reynolds number per foot at these Mach numbers were 6.95 million, 6.42 million, and 4.95 million, respectively. Angle of attack range was -8 to 100 degrees and roll angle was 0 to 315 degrees
Results of an investigation of the 0.003-scale space shuttle external tank MSFC model 460 in the NASA/MSFC 14 x 14-inch Trisonic Wind Tunnel to determine static pressure distributions during reentry (TA2F), volume 5
For abstract, see N76-16132
Results of an investigation of the 0.003-scale space shuttle external tank MSFC model 460 in NASA/MSFC 14 x 14-inch trisonic wind tunnel to determine static pressure distributions during reentry (TA2F), volume 4
For abstract, see N76-16132
Library of medium-resolution fiber optic echelle spectra of F, G, K, and M field dwarfs to giants stars
We present a library of Penn State Fiber Optic Echelle (FOE) observations of
a sample of field stars with spectral types F to M and luminosity classes V to
I. The spectral coverage is from 3800 AA to 10000 AA with nominal a resolving
power 12000. These spectra include many of the spectral lines most widely used
as optical and near-infrared indicators of chromospheric activity such as the
Balmer lines (H_alpha, H_beta), Ca II H & K, Mg I b triplet, Na I D_{1} and
D_{2}, He I D_{3}, and Ca II IRT lines. There are also a large number of
photospheric lines, which can also be affected by chromospheric activity, and
temperature sensitive photospheric features such as TiO bands. The spectra have
been compiled with the goal of providing a set of standards observed at medium
resolution. We have extensively used such data for the study of active
chromosphere stars by applying a spectral subtraction technique. However, the
data set presented here can also be utilized in a wide variety of ways ranging
from radial velocity templates to study of variable stars and stellar
population synthesis. This library can also be used for spectral classification
purposes and determination of atmospheric parameters (T_eff, log{g}, [Fe/H]). A
digital version of all the fully reduced spectra is available via ftp and the
World Wide Web (WWW) in FITS format.Comment: Latex file with 17 pages, 4 figures. Full postscript (text and
figures) available at http://www.ucm.es/info/Astrof/fgkmsl/FOEfgkmsl.html To
be published in ApJ
Measurement of the Hyperfine Structure and Isotope Shifts of the 3s23p2 3P2 to 3s3p3 3Do3 Transition in Silicon
The hyperfine structure and isotope shifts of the 3s23p2 3P2 to 3s3p3 3Do3
transition in silicon have been measured. The transition at 221.7 nm was
studied by laser induced fluorescence in an atomic Si beam. For 29Si, the
hyperfine A constant for the 3s23p2 3P2 level was determined to be -160.1+-1.3
MHz (1 sigma error), and the A constant for the 3s3p3 3Do3 level is -532.9+-0.6
MHz. This is the first time that these constants were measured. The isotope
shifts (relative to the abundant isotope 28Si) of the transition were
determined to be 1753.3+-1.1 MHz for 29Si and 3359.9+-0.6 MHz for 30Si. This is
an improvement by about two orders of magnitude over a previous measurement.
From these results we are able to predict the hyperfine structure and isotope
shift of the radioactive 31Si atom, which is of interest in building a scalable
quantum computer
2S hyperfine structure of atomic deuterium
We have measured the frequency splitting between the and hyperfine sublevels in atomic deuterium by an optical differential
method based on two-photon Doppler-free spectroscopy on a cold atomic beam. The
result Hz is the most precise value for
this interval to date. In comparison to the previous radio-frequency
measurement we have improved the accuracy by the factor of three.
The specific combination of hyperfine frequency intervals for metastable- and
ground states in deuterium atom derived from our measurement is in a good agreement with
calculated from quantum-electrodynamics theory.Comment: 7 pages, 7 figure
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