An official website of the United States government
Here’s how you know
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Principal component analysis (PCA), microbeam X-ray Fluorescence Spectrometry (µXRF), and Monte Carlo simulations are used to illustrate a methodology for assessing the sample microheterogeneity for large sets of materials. PCA is demonstrated to determine
Joseph T. Hodges, David A. Long, Mitchio Okumura, Charles E. Miller
Carbon dioxide (CO2) isotopic ratios were measured at 1.6 μm through the use of frequency-stabilized cavity ring-down spectroscopy (FS-CRDS). We report the highest spectrum signal-to-noise ratios to date for CO2 transitions, with values as high as 28,000:1
Pedro Bueno, Daniel K. Havey, George W. Mulholland, Joseph T. Hodges, Keith A. Gillis, Russell R. Dickerson, Michael R. Zachariah
A quantitative understanding of the absorption and scattering properties of mixed soot and aerosol particles is necessary for evaluating the Earth's energy balance. Uncertainty in the net radiative forcing of atmospheric aerosols is relatively large and
New versions of the NIST Atomic Spectra Database (ASD, v. 4.0) and three bibliographic databases (Atomic Energy Levels and Spectra, v. 2.0, Atomic Transition Probabilities, v. 9.0, and Atomic Line Broadening and Shapes, v. 3.0) have recently been released
Juan C. Collado Gomez, Eduard Rocas, Jordi Mateu, Nathan D. Orloff, James C. Booth, Alberto Padillo, Juan Callaghan
This work proposes a procedure to characterize the intrinsic nonlinearities of bulk acoustic wave resonators by performing one port measurements of the second harmonic and second order intermodulation spurious signals. Closed-form expressions have been
Alexander M. Zolot, Ian R. Coddington, Fabrizio R. Giorgetta, Esther Baumann, William C. Swann, Nathan R. Newbury
A coherent dual comb spectrometer spanning much of the near infrared was constructed from broadened erbium fiber lasers. Gas phase water, methane and acetylene spectra were measured and characterized toward establishing new frequency standards.
Chirantha P. Rodrigo, Christian Muller, Nathan Pillsbury, William H. James III, David F. Plusquellic, Timothy Zwier
The vibronic spectroscopy of jet-cooled bis-(4-hydroxyphenyl)methane (b4HPM) has been explored using fluorescence excitation (FE), dispersed fluorescence (DFL), UV-UV holeburning (UVHB), UV depletion (UVD), and fluorescence-dip infrared (FDIR)
Eyal Gerecht, Kevin O. Douglass, David F. Plusquellic
We report the first demonstration of a broadband trace gas sensor based on chirp-pulse terahertz spectroscopy. The advent of newly developed solid state sources and heterodyne detectors for the terahertz frequency range have made it possible to generate
Frequency combs, like many ground-breaking technologies, are simple in concept; they results from the spectrum of any regular train of optical pulses. What is remarkable is that this simple picture can be actually realized in a number of different
Terrence J. Jach, Fernando D. Vila, W. T. Elam, J. D. Denlinger, John J. Rehr
Non-resonant x-ray emission spectroscopy was used to compare the nitrogen-rich compounds ammonium nitrate, trinitrotoluene, and cyclotrimethylene-trinitramine. They are representative of crystalline and molecular structures of special importance in
Mingdong M. Li, Suvajyoti S. Guha, Rebecca A. Zangmeister, Michael J. Tarlov, Michael R. Zachariah
Electrospray (ES) sources are commonly used to introduce non-volatile materials (e.g. nanoparticles, proteins, etc.) in to the gas phase for characterization by mass spectrometry and ion mobility. Recent studies in our group using electrospray ion mobility
The electronic ground-state potential surface of acetylene (H-CC-H) has a minimum at the linear conformation, but the excited electronic states may have potential minima at a variety of nonlinear equilibrium shapes. This work is concerned with the group
Ion Mobility Spectrometry (IMS) has been used for trace analysis of illicit drugs, but it can also provide reliable qualitative analysis of bulk forensic drug items, despite the complexity of these samples. The drug/drug and drug/excipient combinations
Young Jong Lee, Doyoung Moon, Kalman D. Migler, Marcus T. Cicerone
We demonstrate that broadband coherent anti-Stokes Raman scattering (CARS) microscopy can be very useful for fast acquisition of quantitative chemical images of multilayer polymer blends. Since a raw CARS signal results from coherent interference of
Jason Hattrick-Simpers, Wilbur S. Hurst, James E. Maslar, Sesha S. Srinivasan
An optical cell is described for high-throughput backscattering Raman spectroscopic measurements of hydrogen storage materials at pressures up to 10 MPa and temperatures up to 823 K. High-throughput is obtained by employing a 60 mm diameter x 9 mm thick
Vladimir L. Orkin, Victor Khamaganov, Larissa E. Martynova, Michael J. Kurylo III
Rate constants for the gas phase reactions of OH radicals with ethanol and three fluorinated ethyl alcohols, CH3CH2OH (k0), CH2FCH2OH (k1), CHF2CH2OH (k2), and CF3CH2OH (k3) were measured using a flash photolysis resonance-fluorescence technique over the
Using Raman, Terahertz (THz), and mid-Infrared (IR) spectroscopies, the vibrational spectra of two chromophore models of hydrogen-producing [FeFe]-hydrogenase, Fe2(μ-S2C3H6)(CO)6 and Fe2(μ-S2C2H4)(CO)6, have been assigned. The combination of absorption and
Radu S. Chicireanu, Karl D. Nelson, Steven M. Olmschenk, Nathan Lundblad, A. Derevianko, James V. Porto
We demonstrate substantial cancellation of the differential light shift of a magnetic-field-insensitive microwave hyperfine (clock) transition in 87Rb atoms trapped in an optical lattice. Up to 95.5% of the differential light shift is cancelled while
Hyun M. Kim, Chris A. Michaels, Garnett W. Bryant, Stephan J. Stranick
We experimentally compare the performance and contrast differences between spontaneous and coherent Stokes Raman scattering microscopy. We demonstrate the differences on a series of geometry controlled samples that range in complexity from a point (array
Eduard Rocas, Juan C. Collado Gomez, Nathan D. Orloff, Jordi Mateu, James C. Booth, Juan M. O'Callaghan, Alberto Padilla
AbstractThis article proposes a mechanism by which third-order intermodulation distortion due to self-heating is generated in transmission lines. The work shows how transmission lines made of several materials whose properties are independent of the
This paper is divided into two parts. In the first part an effective Hamiltonian for a non-rotating diatomic molecule containing only crystal-field and spin-orbit operators is set up to describe the energies of the five spin-orbit components that arise in
Nathan R. Newbury, Esther Baumann, Ian R. Coddington, Fabrizio R. Giorgetta, William C. Swann, Alexander M. Zolot
We discuss the performance of a coherent dual frequency comb spectrometer in terms of signal-to-noise ratio, resolution, and accuracy based on experimental data in the near and short-wave infrared centered at 1.5 and 3.4 micrometers.
Clayton Simien, Samuel M. Brewer, Joseph N. Tan, John D. Gillaspy, Craig J. Sansonetti
Precise spectroscopic experiments with light atoms can provide information about nuclear properties that are very difficult to obtain in electron scattering experiments. For example, relative nuclear radii of low-Z isotopes can be determined accurately