Experimental determination of the 6s^2 ^1S_0 -> 5d6s ^3 D_1 magnetic-dipole transition amplitude in atomic ytterbium

We report on a measurement of the highly forbidden 6s^2 ^1S_0 \to 5d6s ^3 D_1 magnetic-dipole transition in atomic ytterbium using the Stark-interference technique. This amplitude is important in interpreting a future parity nonconservation experiment that exploits the same transition. We find $| | ~ = ~ 1.33(6)_{Stat}(20)_{\beta} \times 10^{-4} \mu_0$, where the larger uncertainty comes from the previously measured vector transition polarizability $\beta$. The $M1$ amplitude is small and should not limit the precision of the parity nonconservation experiment.Comment: 4 pages, 5 figures Paper resubmitted with minor corrections and additions based on comments from referee

Polarizabilities and parity non-conservation in the Cs atom and limits on the deviation from the standard electroweak model

A semi-empirical calculation of the 6s - 7s Stark amplitude $\alpha$ in Cs has been performed using the most accurate measurements and calculations of the electromagnetic amplitudes available. This is then used to extract the parameters of the electroweak theory from experimental data. The results are: $\alpha = 269.0 (1.3) a_0^3$, weak charge of Cs $Q_W = -72.41(25)_{exp} (80)_{theor}$, deviation from the Standard model $S = -1.0(.3)_{exp} (1.0)_{theor}$ and limit on the mass of the extra Z-boson in SO(10) model $M_{Z_x} > 550 GeV$.Comment: 8 pages; submitted to Phys. Rev.

Attention bias to emotional faces varies by IQ and anxiety in Williams syndrome

Individuals with Williams syndrome (WS) often experience significant anxiety. A promising approach to anxiety intervention has emerged from cognitive studies of attention bias to threat. To investigate the utility of this intervention in WS, this study examined attention bias to happy and angry faces in individuals with WS (N=46). Results showed a significant difference in attention bias patterns as a function of IQ and anxiety. Individuals with higher IQ or higher anxiety showed a significant bias toward angry, but not happy faces, whereas individuals with lower IQ or lower anxiety showed the opposite pattern. These results suggest that attention bias interventions to modify a threat bias may be most effectively targeted to anxious individuals with WS with relatively high IQ

Local- and regional-scale measurements of CH₄, δ¹³CH₄, and C₂H₆ in the Uintah Basin using a mobile stable isotope analyzer

In this paper, we present an innovative CH₄, δ¹³CH₄, and C₂H₆ instrument based on cavity ring-down spectroscopy (CRDS). The design and performance of the analyzer is presented in detail. The instrument is capable of precision of less than 1 ‰ on δ¹³CH₄ with 1 in. of averaging and about 0.1 ‰ in an hour. Using this instrument, we present a comprehensive approach to atmospheric methane emissions attribution. Field measurements were performed in the Uintah Basin (Utah, USA) in the winter of 2013, using a mobile lab equipped with the CRDS analyzer, a high-accuracy GPS, a sonic anemometer, and an onboard gas storage and playback system. With a small population and almost no other sources of methane and ethane other than oil and gas extraction activities, the Uintah Basin represents an ideal location to investigate and validate new measurement methods of atmospheric methane and ethane. We present the results of measurements of the individual fugitive emissions from 23 natural gas wells and six oil wells in the region. The δ¹³CH₄ and C₂H₆ signatures that we observe are consistent with the signatures of the gases found in the wells. Furthermore, regional measurements of the atmospheric CH₄, δ¹³CH₄, and C₂H₆ signatures throughout the basin have been made, using continuous sampling into a 450 m long tube and laboratory reanalysis with the CRDS instrument. These measurements suggest that 85 ± 7 % of the total emissions in the basin are from natural gas production

Calibrated high-precision O-17-excess measurements using cavity ring-down spectroscopy with laser-current-tuned cavity resonance

High-precision analysis of the 17O / 16O isotope ratio in water and water vapor is of interest in hydrological, paleoclimate, and atmospheric science applications. Of specific interest is the parameter 17O excess (&Delta;17O), a measure of the deviation from a~linear relationship between 17O / 16O and 18O / 16O ratios. Conventional analyses of &Delta;17O of water are obtained by fluorination of H2O to O2 that is analyzed by dual-inlet isotope ratio mass spectrometry (IRMS). We describe a new laser spectroscopy instrument for high-precision &Delta;17O measurements. The new instrument uses cavity ring-down spectroscopy (CRDS) with laser-current-tuned cavity resonance to achieve reduced measurement drift compared with previous-generation instruments. Liquid water and water-vapor samples can be analyzed with a better than 8 per meg precision for &Delta;17O using integration times of less than 30 min. Calibration with respect to accepted water standards demonstrates that both the precision and the accuracy of &Delta;17O are competitive with conventional IRMS methods. The new instrument also achieves simultaneous analysis of δ18O, &Delta;17O and &delta;D with precision of < 0.03&permil;, < 0.02 and < 0.2&permil;, respectively, based on repeated calibrated measurements

Evaluation of the IAGOS-Core GHG package H₂O measurements during the DENCHAR airborne inter-comparison campaign in 2011

As part of the DENCHAR (Development and Evaluation of Novel Compact Hygrometer for Airborne Research) inter-comparison campaign in northern Germany in 2011, a commercial cavity ring-down spectroscopy (CRDS) based gas analyzer (G2401-m, Picarro Inc., US) was installed on a Learjet to measure atmospheric water vapor, CO2, CH4, and CO. The CRDS components were identical to those chosen for integration aboard commercial airliners within the IAGOS (In-service Aircraft for a Global Observing System) project. Since the quantitative capabilities of the CRDS water vapor measurements were never evaluated and reviewed in detail in a publication before, the campaign allowed for an initial assessment of the long-term IAGOS water vapor measurements by CRDS against reference instruments with a long performance record (Fast In-situ Stratospheric Hygrometer (FISH) and CR-2 frost point hygrometer (Buck Research Instruments L.L.C., US), both operated by Research Centre Jülich).For the initial water calibration of the instrument it was compared against a dew point mirror (Dewmet TDH, Michell Instruments Ltd., UK) in the range from 70&thinsp;000 to 25&thinsp;000&thinsp;ppm water vapor mole fraction. During the inter-comparison campaign the analyzer was compared on the ground over the range from 2 to 600&thinsp;ppm against the dew point hygrometer used for calibration of the FISH reference instrument. A new, independent calibration method based on the dilution effect of water vapor on CO2 was evaluated.Comparison of the in-flight data against the reference instruments showed that the analyzer is reliable and has a good long-term stability. The flight data suggest a conservative precision estimate for measurements made at 0.4&thinsp;Hz (2.5&thinsp;s measurement interval) of 4&thinsp;ppm for H2O&thinsp;&lt;&thinsp;10&thinsp;ppm, 20&thinsp;% or 10&thinsp;ppm (whichever is smaller) for 10&thinsp;ppm&thinsp;&lt;&thinsp;H2O&thinsp;&lt;&thinsp;100&thinsp;ppm, and 5&thinsp;% or 30&thinsp;ppm (whichever is smaller) for H2O&thinsp;&gt;&thinsp;100&thinsp;ppm. Accuracy of the CRDS instrument was estimated, based on laboratory calibrations, as 1&thinsp;% for the water vapor range from 25&thinsp;000&thinsp;ppm down to 7000&thinsp;ppm, increasing to 5&thinsp;% at 50&thinsp;ppm water vapor. Accuracy at water vapor mole fractions below 50&thinsp;ppm was difficult to assess, as the reference systems suffered from lack of data availability.</p