National Institute of Standards and Technology

About: National Institute of Standards and Technology is a government organization based out in Gaithersburg, Maryland, United States. It is known for research contribution in the topics: Laser & Scattering. The organization has 26667 authors who have published 60661 publications receiving 2215547 citations. The organization is also known as: National Bureau of Standards & NIST.

Spectroscopic observation of SU(N)-symmetric interactions in Sr orbital magnetism

Abstract: Physicists have used cold atomic gases to simulate quantum phenomena that we normally associate with much more complex systems, such as solid-state materials. Because the properties of these gases are so tunable, it is also possible to create conditions that otherwise do not exist in nature. Zhang et al. studied an exotic type of magnetism in an array of pancake-shaped atomic clouds of 87Sr. They prepared the atoms' nuclei in different combinations of 10 quantum states. They then shone pulses of light at the atoms to deduce the properties of the atoms' interactions. The interactions were independent of the atoms' nuclear states—a hallmark of an unusual symmetry that theorists predict may lead to interesting collective effects. Science , this issue p. [1467][1] [1]: /lookup/doi/10.1126/science.1254978

Phase-Separation-Induced Surface Patterns in Thin Polymer Blend Films

Abstract: Atomic force microscopy (AFM), neutron reflection (NR) and secondary ion mass spectroscopy (SIMS) are used to examine phase separation in symmetrically segregating thin polymer blend films (≤1000 A). Phase separation in the film leads to undulations of the liquid−air interface, provided the film is sufficiently thin to suppress surface-directed spinodal decomposition waves. Flattened droplets are formed at a very late stage of phase separation, and the aspect ratio of these droplets can be rationalized by an interfacial free energy minimization argument.

Frequency-comb-based remote sensing of greenhouse gases over kilometer air paths

Abstract: Increasing our understanding of regional greenhouse gas transport, sources, and sinks requires accurate, precise, continuous measurements of small gas enhancements over long ranges. We demonstrate a coherent dual frequency-comb spectroscopy technique capable of achieving these goals. Spectra are acquired spanning 5990 to 6260 cm−1 (1600–1670 nm) covering ∼700 absorption features from CO2, CH4, H2O, HDO, and CO213, across a 2 km path. The spectra have sub-1-kHz frequency accuracy, no instrument lineshape, and a 0.0033 cm−1 point spacing. They are fit with different absorption models to yield dry-air mole fractions of greenhouse gases. These results are compared with a point sensor under well-mixed conditions to evaluate the accuracy of models critical to global satellite-based trace gas monitoring. Under heterogeneous conditions, time-resolved data demonstrate tracking of small variations in mole fractions, with a precision <1 ppm for CO2 and <3 ppb for CH4 in 5 min. Portable systems could enable regional monitoring.

A Rigorous Attempt to Verify Interstellar Glycine

Abstract: In 2003, Kuan, Charnley, and co-workers reported the detection of interstellar glycine (NH2CH2COOH) based on observations of 27 lines in 19 different spectral bands in one or more of the sources Sgr BP(N-LMH), Orion KL, and W51 e1/e2. They supported their detection report with rotational temperature diagrams for all three sources. In this paper, we present essential criteria which can be used in a straightforward analysis technique to confirm the identity of an interstellar asymmetric rotor such as glycine. We use new laboratory measurements of glycine as a basis for applying this analysis technique, both to our previously unpublished 12 m telescope data and to the previously published SEST data of Nummelin and colleagues. We conclude that key lines necessary for an interstellar glycine identification have not yet been found. We identify several common molecular candidates that should be examined further as more likely carriers of the lines reported as glycine. Finally, we illustrate that rotational temperature diagrams used without the support of correct spectroscopic assignments are not a reliable tool for the identification of interstellar molecules. Subject headings: ISM: abundances - ISM: clouds - ISM: individual (Sagittarius B2[N-