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Search Publications by: Howard W. Yoon (Fed)

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Displaying 1 - 25 of 141

Radiative Decay Rate and Branching Fractions of MgF

September 8, 2023
Eric Norrgard, Catherine Cooksey, Stephen Eckel, Nickolas Pilgram, Kayla Rodriguez, Howard W. Yoon, Yuly Andrea Chamorro Mena, Lukas Pasteka, Anastasia Borschevsky
Here we report measured and calculated values of radiative decay rates and vibrational branching fractions for the A$^2\Pi$ state of MgF. The decay rate measurements use time-correlated single photon counting with roughly 1\,\% total uncertainty. Branching

ITS10 Conference Digest

April 18, 2023
Christopher W. Meyer, Kathryn Miller, Weston L. Tew, Howard W. Yoon
The 10th International Temperature Symposium (ITS10) was held in Anaheim California on April 3rd to 7th, 2023. More than 180 abstracts were received and accepted and 159 of those were presented at the symposium. This document is a record of the symposium

Characterization and Absolute Calibration of an AERONET-OC Radiometer

April 15, 2021
B. Carol Johnson, Giuseppe Zibordi, Steven W. Brown, Michael Feinholz, Mikhail Sorokin, Ilya Slutsker, John T. Woodward IV, Howard Yoon
The Ocean Color component of the global Aerosol Robotic Network (AERONET-OC) utilizes CE-318 sun photometers modified for above-water radiometry from fixed structures such as oil rigs, lighthouses, and service platforms. Primarily, AERONET-OC measurements

Nonlinear Response of Silicon Solar Cells

January 1, 2019
Behrang H. Hamadani, Andrew M. Shore, Howard W. Yoon, Mark Campanelli
We used an LED-array-based combinatorial flux addition method to explore the wavelength and the intensity-dependence of the spectral responsivity in silicon solar cells. Many types of silicon cells, whether mono- or multi-crystalline type, exhibit notable

Invited Article: Advances in Tunable Laser-based Radiometric Calibration Applications at the National Institute of Standards and Technology, USA

September 26, 2018
John T. Woodward IV, Ping-Shine Shaw, Howard Yoon, Yuqin Zong, Steven W. Brown, Keith R. Lykke
Recent developments at the National Institute of Standards and Technology's facility for Spectral Irradiance and Radiance responsivity Calibrations using Uniform Sources (SIRCUS) are presented. The facility is predicated on the use of broadly tunable

Broadband Radiometric LED Measurements

September 6, 2016
George P. Eppeldauer, P. Yvonne Barnes, Howard W. Yoon, Leonard Hanssen, Vyacheslav B. Podobedov, Robert E. Vest, Uwe Arp, C Cameron Miller
At present, broadband radiometric measurements of LEDs with uniform and low-uncertainty results are not available. Currently, either spectral radiometric measurements or broadband photometric LED measurements are used. The broadband photometric

Advances in Thermometry

January 1, 2016
Michael R. Moldover, Weston L. Tew, Howard W. Yoon
The last 25 years have seen tremendous progress in thermometry in the moderate temperature range (1 K to 1235 K). Various primary thermometers — based on different physics —have uncovered errors in the International Temperature Scale of 1990 and set the

Calibration procedure for UV-365 integrated irradiance measurements

September 8, 2015
George P. Eppeldauer, Thomas C. Larason, Robert E. Vest, Uwe Arp, Howard W. Yoon
Since the CIE standardized rectangular-shape spectral response function for the 320 nm to 400 nm wavelength range can be realized only with large spectral mismatch, the realized UV-A meters have different response functions resulting in large errors in

Standardization of UV LED measurements

September 8, 2015
George P. Eppeldauer, Thomas C. Larason, Howard W. Yoon
Traditionally used source spectral-distribution or detector spectral-response based standards cannot be applied for accurate UV LED measurements. Since the CIE standardized rectangular-shape spectral response function for UV measurements cannot be realized

Principles of Optical Radiometry and Measurement Uncertainty

November 27, 2014
Bettye C. Johnson, Howard W. Yoon, Joseph P. Rice, Albert C. Parr
The fundamental concepts of optical radiometry are developed from basic principles, with detailed explanations for radiance, irradiance, and reflectance. Examples of radiometric standards, in particular radiometers and reference sources are given, and the

IR-enhanced Si reference detectors for 1-step scale transfers from 300 nm to 1000 nm

November 20, 2014
George P. Eppeldauer, Thomas C. Larason, Jeanne M. Houston, Robert E. Vest, Uwe Arp, Howard W. Yoon
IR-enhanced Si photodiodes have improved radiometric and electronic characteristics as compared to other widely used Si photodiodes and can be used as responsivity standards in the wavelength range from 300 nm to 1000 nm. Their low predicted uncertainty

Challenges of Irradiance-mode Spectral Response Measurements

October 16, 2014
Behrang H. Hamadani, John F. Roller, Brian P. Dougherty, Howard W. Yoon
Irradiance-mode spectral response measurements of solar cells are important because they provide a direct, reliable and accurate route for determination of the short circuit current (Isc) of solar cells under air mass 1.5 standard reference spectrum. In

Dispersive Methods

July 1, 2014
Arnold A. Gaertner, Howard Yoon, Thomas Germer
Chapter 3 will discuss dispersive means of obtaining spectral resolution in spectrophotometry. These methods are used to spatially disperse or separate the various wavelengths of optical electromagnetic radiation to enable analysis of material properties

Large-area irradiance-mode spectral response measurements of solar cells by a light-emitting-diode- based integrating sphere source

May 30, 2014
Behrang H. Hamadani, John F. Roller, Andrew M. Shore, Brian P. Dougherty, Howard W. Yoon
An irradiance-mode absolute differential spectral response measurement system based on a light emitting diode (LED) array is described. The LEDs are coupled to an integrating sphere whose output irradiance is uniform to better than 2 % over an area of 160

Sensor Calibration and Characterization to Meet Climate Monitoring Requirements

April 24, 2014
Catherine C. Cooksey, Gerald T. Fraser, Howard W. Yoon
The challenge of detecting small changes in the Earth's climate system over decadal and longer time scales places stringent requirements on environmental monitoring systems. Sensors must be well calibrated and maintain their calibration in challenging

Fast and Reliable Spectral Response Measurements of PV Cells Using Light Emitting Diodes

January 1, 2014
Behrang H. Hamadani, John F. Roller, Brian P. Dougherty, Howard W. Yoon
We present a measurement system for absolute differential spectral responsivity of solar cells based on high-powered LED arrays coupled to an optical light guide capable of large area illumination. Two different measurement techniques were developed and