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Search Publications by: Joseph T. Hodges (Fed)

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Displaying 51 - 75 of 106

Differential cavity ring-down spectroscopy

May 9, 2013
Author(s)
Jeremie B. Courtois, Katarzyna E. Bielska, Joseph T. Hodges
We present a technique called differential cavity ring-down spectroscopy (D-CRDS) for reducing etaloning effects in a ring-down spectrometer. The method relies on alternately measuring and then subtracting intra-cavity losses associated with pairwise TEM00

Frequency-agile, rapid scanning spectroscopy

April 28, 2013
Author(s)
Gar W. Truong, Kevin O. Douglass, Stephen E. Maxwell, Roger D. van Zee, David F. Plusquellic, Joseph T. Hodges, David A. Long
Challenging applications in trace gas analyses require high precision and acquisition rates.1-4 Many continuous-wave laser spectroscopy techniques exhibit significant sensitivity and potential;5 however, their scanning rates are slow because they rely upon

Coupled-cavity ring-down spectroscopy technique

August 6, 2012
Author(s)
Jeremie B. Courtois, Joseph T. Hodges
We present a technique called coupled-cavity ring-down spectroscopy (CC-RDS) for controlling the finesse of an optical resonator. Applications include extending the sensitivity and dynamic range of a cavity-enhanced spectrometer, as well as widening the

Frequency-stabilized cavity ring-down spectroscopy

March 21, 2012
Author(s)
David A. Long, A. Cygan, Roger D. van Zee, Mitchio Okumura, C. E. Miller, D Lisak, Joseph T. Hodges
This Frontiers article describes frequency-stabilized cavity ring-down spectroscopy (FS-CRDS), an ultraprecise refinement of conventional cw-CRDS. We review the technique and highlight some recent studies which have utilized FS-CRDS to perform precision

Spectroscopic Measurement of the Vapour Pressure of Ice

January 1, 2012
Author(s)
Katarzyna E. Bielska, Daniel K. Havey, Gregory E. Scace, D Lisak, Joseph T. Hodges
We present a laser absorption technique to measure the vapor pressure of ice. This method is referenced to the triple point state of water and uses frequency-stabilized cavity ring-down spec- troscopy to probe four rotation-vibration transitions of H16 2 O

Construction of a High Power OPO Laser system for Differential Absorption LIDAR

September 13, 2011
Author(s)
Kevin O. Douglass, Stephen E. Maxwell, David F. Plusquellic, Joseph T. Hodges, Roger D. van Zee, Daniel V. Samarov, James R. Whetstone
Our goal is to develop and characterize optical measurement technology to enable accurate quantification of greenhouse-gas emissions to meet the needs of industry and regulators. A 1064 nm pumped high energy optical parametric oscillator (OPO) operating

PDH-locked, frequency-stabilized cavity ring-down spectrometer

June 16, 2011
Author(s)
Joseph T. Hodges, A. Cygan, Piotr Maslowski, Katarzyna E. Bielska, S. Wojtewicz, J. Domyslawska, Hisashi Abe, R.S. Trawinski, R. Ciurylo
We describe a high sensitivity and high spectral resolution laser absorption spectrometer based upon the frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) technique. We used the Pound-Drever-Hall (PDH) method to lock the probe laser to the high

Amplification of the optical absorption cross section for aerosols of soot with a nonabsorbing coating from photoacoustic measurements

May 13, 2011
Author(s)
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

Standard Photoacoustic Spectrometer: Model and Validation using O2 A-Band Spectra

June 30, 2010
Author(s)
Keith A. Gillis, Daniel K. Havey, Joseph T. Hodges
We model and measure the absolute response of an intensity-modulated photoacoustic spectrometer comprising a 10 cm long resonator and having a Q-factor of approximately 30. We present a detailed theoretical analysis of the system and predict its response

A Second-Generation NIST Gravimetric Hygrometer

April 1, 2010
Author(s)
Christopher W. Meyer, Joseph T. Hodges, Gregory E. Scace, James R. Whetstone, R W. Hyland
A second-generation primary hygrometer has been completed at the National Institute of Standards and Technology (NIST). A gravimetric hygrometer measures humidity by separating the water from the carrier gas using desiccants and afterwards independently

Ultra-Sensitive Optical Measurements of High-J Transitions in the O2 A-band

November 24, 2009
Author(s)
Daniel K. Havey, Joseph T. Hodges, David A. Long, Mitchio Okumura, Charles E. Miller
We report frequency-stabilized cavity ring-down spectroscopy measurements of high-J O2 A-band magnetic dipole line parameters. Our goals were to measure intensities and line shape parameters for the primary isotopologue of O2 in the A-band region and to

Calibration of Hygrometers with the Hybrid Humidity Generator

December 14, 2008
Author(s)
Christopher W. Meyer, Joseph T. Hodges, Peter H. Huang, W Wyatt Miller, Dean C. Ripple, Gregory E. Scace
We describe here the calibration of customer hygrometers using a new humidity generator that has been commissioned at the National Institute of Standards and Technology. The NIST Hybrid Humidity Generator (HHG) generates frost/dew points from –70 °C to +85

Automated Continuous-Flow Gravimetric Hygrometer as a Primary Humidity Standard

May 1, 2008
Author(s)
Christopher W. Meyer, Joseph T. Hodges, R W. Hyland, Gregory E. Scace, J Valencia-Rodriguez, James R. Whetstone
A new primary gravimetric hygrometer has been completed at the National Institute of Standards and Technology (NIST). This apparatus determines the humidity in a steadily flowing gas stream by first separating the water from the carrier gas using

High Temperature Electrical Resistance of substrate-supported Single Walled Carbon Nanotubes

January 1, 2008
Author(s)
Richard E. Cavicchi, C Avedisian, Paul M. McEuen, Xinjian Zhou, Wilbur S. Hurst, Joseph T. Hodges
We report the electrical characteristics of two substrate-supported metallic single walled carbon nanotubes (SWNT) at temperatures up to 573 K over a range of bias voltages for zero gate voltage in air under atmospheric pressure. At low voltages or high

In Situ Gas Phase Diagnostics for Hafnium Oxide Atomic Layer Deposition

January 1, 2008
Author(s)
James E. Maslar, Wilbur S. Hurst, Donald R. Burgess Jr., William A. Kimes, Nhan V. Nguyen, Elizabeth F. Moore, Joseph T. Hodges
Atomic layer deposition (ALD) is an important method for depositing the nanometer-scale, conformal high  dielectric layers required for many nanoelectronics applications. In situ monitoring of ALD processes has the potential to yield insights that will