An official website of the United States government

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.

# James A. Fedchak (Fed)

Jim Fedchak has been with NIST since 2003. He leads the vacuum project, which includes realizing and disseminating absolute pressures from 10-7 Pa to 30 Pa, and low gas flow from 10-12 mol/s to 10-6 mol/s. He is directly responsible for ionization gauge calibrations and spinning rotor gauge calibrations. Jim's knowledge of vacuum science and technology covers a variety of applications derived from his previous work experience. Previously, Jim worked with the Low-background Infrared Radiation project at NIST doing cryogenic infrared radiometry; worked in the photonics industry with New Focus Inc.; performed atomic spectroscopy at the University of Wisconsin; and developed spin-polarized targets at Argonne National Laboratory. He has a PhD in experimental atomic and molecular physics from the College of William and Mary. He has numerous publications in all of these fields. Jim is a member of the Low Pressure Working Group of the CCM, and is presently a member of the AVS Vacuum Technology Division Committee.

## Publications

### A constant pressure flowmeter for the extremely high vacuum

Author(s)
Stephen Eckel, Daniel Barker, James A. Fedchak, Emmanuel Newsome, Julia Scherschligt, Robert E. Vest
We demonstrate operation of a constant-pressure flowmeter capable of generating and accurately measuring flows as low as $1\times10^-13}$mol/s. Generation of

### Comparison of two multiplexed portable cold atom vacuum standards

Author(s)
Lucas Ehinger, Bishnu Acharya, Daniel Barker, James A. Fedchak, Julia Scherschligt, Eite Tiesinga, Stephen Eckel
We compare the vacuum measured by two portable cold atom vacuum standards (pCAVS) based on ultracold $^7$Li atoms. Our pCAVS devices share the same laser system

### Erratum: Elastic Rate Coefficients of Li + H_2 collisions in the calibration of a Cold Atom Vacuum Standard

Author(s)
Constantinos Makrides, Daniel Barker, James A. Fedchak, Julia Scherschligt, Stephen Eckel, Eite Tiesinga
We found an error in our computation of the thermally averaged total rate coefficients for the collision of a room-temperature hydrogen dimer H$_2$ with an

### Lambda-enhanced gray molasses in a tetrahedral laser beam geometry

Author(s)
Daniel Barker, Eric Norrgard, Nikolai Klimov, James A. Fedchak, Julia Scherschligt, Stephen Eckel
We report observation of sub-Doppler cooling of lithium using an irregular-tetrahedral laser beam arrangement, which is produced by a nanofabricated diffraction

### Erratum: Collisions of room temperature helium with ultra-cold lithium and the van-der-Waals bound state of HeLi [Phys. Rev. A 101, 012702 (2020)]

Author(s)
Constantinos Makrides, Daniel Barker, James A. Fedchak, Julia Scherschligt, Stephen Eckel, Eite Tiesinga
We have found an error in the computation of the thermally-averaged total elastic rate coefficient for the collision of a room-temperature helium atom with an

## Patents

### OPTOMECHANICAL PRESSURE MEASUREMENT SYSTEM AND METHOD USING THE VIBRATIONAL MODES OF A MEMBRANE

NIST Inventors
Stephen Eckel , James A. Fedchak , Thomas Purdy and Robinjeet Singh

### UNIAXIAL COUNTER-PROPAGATING MONOLASER ATOM TRAP

NIST Inventors
Stephen Eckel , James A. Fedchak , Julia Scherschligt , Daniel Barker and Eric Norrgard
Created October 9, 2019, Updated December 5, 2022