The NBS/NIST Microwave Laboratory

Location:
        National Bureau of Standards, Washington, USA
        National Institute of Standards and Technology. Gaithersburg, USA

Key Scientists:
        Frank Lovas, David Lide, Rick Suenram, Don Johnson, Gerald Fraser, Walter Lafferty

Overview:
       This influential rotational spectroscopy laboratory operated, unlike university laboratories, under the rigors of an institution dedicated to applied science.  The origins of the laboratory can be traced back to 1954, when David Lide was hired by NBS to start research using the Stark modulation technique. After the formative period the work at NBS (later rebranded as NIST) became strongly associated with the fields of atmospheric chemistry and molecular radio astronomy. Some notable results are many publications in the Journal of Physical and Chemical Reference Data (edited for many years by David Lide) and several open access computer databases at NIST established by Frank Lovas.  Equally notable results are concerted laboratory and radioastronomy work on new astrophysical molecules.

       The NIST laboratory was also active in the development of the second generation of the Fourier Transform Microwave (FTMW) spectrometer. Their design evolved into a patented portable spectrometer optimised for chemical analysis. As with all other rotational spectrometers this was still too complex for industrial use, but several copies were produced for university laboratories. This type of spectrometer was the tool for many groundbreaking contributions from NIST made in the field of small van der Waals and hydrogen bonded clusters.


Documents:

NBS/NIST history History of the NBS/NIST Microwave Laboratory by Lovas, Lide, Suenram, Johnson
History of the NBS/NIST laboratory HTML version of the History of the NBS/NIST Microwave Laboratory and additional quick links to its sections:
    Title page, Introduction,
    Development of microwave spectroscopy at NBS,
    Specific Studies from 1954 to the Early 1970s,
    Applications in Radio Astronomy and Atmospheric Chemistry,
    Fabry-Perot Cavity Fourier Transform Microwave Spectrometer,
    References
portable FTMW patent US Patent 5831439 describing the "Portable Fourier Transform Microwave Spectrometer with Cryogenic Receiver for Trace Gas Analysis"

 

Picture gallery:

Select any picture with the mouse to enter the gallery mode. Successive pictures can then be conveniently inspected in various ways, also by using the mouse scroll wheel.

David Lide, the originator of the microwave spectroscopy program at NBS (photo circa 1960). The main spectrometer in the NBS microwave lab in 1957, with David Lide operating the controls. Two waveguide absorption cells are in the bottom center; the left cell is in an insulated trough that could be cooled with dry ice. Stark modulation with an 80 kHz square wave was applied to a septum in the cells. Spectra were usually observed and measured on the oscilloscope, with the chart recorder used for fine details. Allen Astin, NBS Director, presenting the Stratton Award to David Lide in 1968. The citation is: 'For outstanding research and distinguished authorship in the field of microwave spectroscopy'. The Samuel Wesley Stratton Award is presented annually to a NIST (NBS) employee or group 'To recognize outstanding scientific or engineering achievements in support of NIST objectives'. Walt Lafferty, who joined the combined infrared-microwave NBS group in the early 1960's. Passport photo from 1967. Technician measuring in NBS MW lab, around 1969. His right hand is on a variac which controls the squarewave amplitude for Stark modulation. The signal on the scope looks like 1st order Stark lobes (up) and zero field absorption (down). His left hand is on radio receiver tuned to 80 kHz. Francis X. Powell (right) and Don Johnson (left) in the new laboratory space at the Gaithersburg site, around 1969. The parallel plate Stark cell is visible at bottom right, with sample handling glass vacuum line above it. The black unit at lower right is an oil bath can containing the klystron. The millimeter wave parallel plate Stark cell used at frequencies from 40 GHz to GHz, and in measurements including those on ClO, BrO, SF2, H2CS, CH2NH, CH2, HOCl, ClNO3 and HOONO2. The sample inlet port, top left and exit port bottom right, allowed sample to be flowed directly between the two electrodes. The cell was constructed in 1969 and was made entirely of glass and gold-coated metal to minimize decomposition the radicals and transient species. The quartz sample inlet tube allowed a microwave cavity (Evanson design) to be attached in order to make a microwave discharge in the flowing sample gas. Centimeter wave parallel plate Stark cell, around 1977. This was used at frequencies 4 GHz - 60 GHz, and for studies of such transient species the SO-dimer, OSSO, S2O and vinylamine as well as stable species. Lew Snyder at the console of the NRAO 140 ft radio telescope at Green Bank, WV (around 1975). Can you count the number of politically incorrect things he is doing here? From the left: Don Johnson, Frank Clark, Richard Pearson, and Frank Lovas (NBS Gaithersburg, MD around 1974). Don Johnson (left) and Frank Lovas (right) after being awarded the Department of Commerce Gold Medal in 1976, the highest award in the Department. Gold Medal Citation: For the outstanding contributions to the interdisciplinary application of microwave spectroscopic techniques to aeronomy, astronomy, chemistry, and industry. Ku-band (12-18 GHz) stainless steel Stark septum cell (constructed by Lovas and Suenram) with liquid nitrogen cooling jacket (around 1977) used in the study of the ozone-ethylene reaction products, the primary ozonide of ethylene and dioxirane. Several variations were tried in condensing the reactants on the cell walls at liquid nitrogen temperature (-196 °C) in order to prevent explosive reaction. The best method found was to pressurize the cell with about 1 Torr of ozone, cool the cell with liquid nitrogen, and pump off any residual oxygen that did not freeze out. Then the ethylene was introduced via a needle valve for about 15 s, keeping the inlet line pressure between 50 to 100 mTorr. This provided a thin layer coating over a large area of the cell. Instead of using a liquid nitrogen trap in front of the diffusion pump, where unreacted material could concentrate and cause an explosive reaction, a trap filled with copper turnings and heated to 100 °C destroyed any ozone and other reactive species formed in the cell. Thus a high degree of caution is advised in studying the ozone-olefin reactions. Reproduced from M. Jacobs, NBS Dimensions, pp 3-7 Nov. 1977. The structure and the proposed mechanism of formation of dioxirane, studied by Suenram and Lovas in 1978. This molecule is directly related to the H2COO 'Criegee' radical, an intermediate of relevance to urban smog formation. During one of the searches for interstellar glycine carried out in the 1980's at Green Bank, WV, Rick Suenram assisted in pointing the NRAO 140 ft. telescope (photo by Lovas). The setup that was used to generate the CH2 radical. Microwave discharge of F2 in He, produced F atoms that were used to extract hydrogen atoms from methane. Three hyperfine multiplets were observed in the mm-wave region (1983) and interstellar CH2 was eventually observed in 1995 by Hollis, Jewell, and Lovas toward the Orion-KL and W51 M molecular clouds. One of the Fabry-Perot resonator mirrors in the NIST FTMW spectrometer described in 1987. Mirror movement was achieved by means of manually stepping the motor micrometers behind each mirror. In the 1990’s the mirror movement was computer controlled for automated spectral searches. Alan Pine (left) and Jerry Fraser standing next to the microwave and infrared electric-resonance optothermal (EROS) spectrometer about 1989. This spectrometer was described in G.T. Fraser and A.S. Pine, J. Chem. Phys. 91, 637 (1989). The reaction coordinate from ethylene+ozone to ethylene primary ozonide studied by Gillies and Gillies during extended visits in the NBS microwave lab in 1987-1988. Stew Novick at the NBS FTMW spectrometer during sabbatical leave from Wesleyan University in 1988. He is moving the Fabry Perot cavity mirror with the motor-mike control in his right hand and starting the TTL pulse sequence controlling the microwave switches and pulsed nozzle with the left hand, while enjoying unspecified audio. Schematic diagram of the portable FTMW spectrometer developed at NIST in the mid to late 1990s. Keiji Matsumura using the original FTMW spectrometer while on sabbatical from Seinan Gakuin University in Japan (1990). Several pulsed nozzle designs for the FTMW spectrometer developed by Suenram and Lovas in the 1990's. The polar corannulene molecule studied by Lovas and Grabow (results published in 2005) which proved to be an extreme test of the heated expansion nozzle design. The required nozzle temperatures of 220-250oC were obtained at the cost of several burnt out nozzle coils. The laser ablation pulsed nozzle source used to study refractory materials or other low vapor pressure solids. The first studies involved SiC2 (1989), YO, LaO, ZrO, HfO (1990), BaO and SrO (1992). Rick Suenram with Andrey Zuban (middle) and Igor Leonov (right). Andrey and Igor were outstanding hardware and software specialists and in 1998 developed a software package allowing unattended searches spanning many GHz to be performed with the FTMW spectrometer. Angie Hight Walker, a Postdoctoral fellow with Rick Suenram (1994-1996) with one of the portable type FTMW spectrometers at NIST. Frank Lovas, Mike Hollis and Phil Jewel (left to right) at the NRAO 12 m in May 2000 during the search for and detection of glycolaldehyde. Formation route for the cyclopropenone molecule via the addition of an oxygen atom to cyclopropenylidine (c-C3H2). Interstellar cyclopropenone was detected in 2006 by Hollis, Remijan, Jewell and Lovas using the NRAO 100 m Green Bank Telescope (GBT). Jan (Mike) Hollis, Anthony Remijan, and Philip Jewell (left to right) in the GBT control room, 2004 (taken by Lovas). View of the NRAO 140 ft. radiotelescope from top of the receiver room of the GBT (2005). Only a small part of the 100 m GBT dish is in view at the bottom half of photo (photo taken by Lovas). Kevin Douglass, at NIST from 2007 involved in development of broadband, terahertz chirped pulse spectroscopy. David Plusquellic, at NIST from the mid 1990's, developer of the JB95 program for efficient analysis of rotational spectra. He is currently (2012) involved in development of broadband, terahertz chirped pulse spectroscopy and is pictured next to the high speed oscilloscope used for averaging the free induction decay signals.

Photo Credits: F.J. Lovas, D.R. Lide Jr., R.D. Suenram, D.R. Johnson, "Evolution of Microwave Spectroscopy at the National Bureau of Standards (NBS) and the National Institute of Standards and Technology (NIST)" (2012).