Pulsed Nozzle Fourier Transform Microwave Spectrometer: Advances and Applications (original) (raw)
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Journal of research of the National Institute of Standards and Technology
he developed parallel plate cells coupled with rf and DC discharge methods to study free radicals and transient species. In the mid 1980s Lovas and Suenram constructed a pulsed molecular beam Fourier Transform microwave (FTMW) spectrometer to study hydrogen bonded and van der Waals dimers and trimers. This article describes the types of molecules studied and the type molecular properties derived from these measurements as well as some of the instruments developed for these studies. The two major areas of application described are atmospheric chemistry and molecular radio astronomy.
Scanning Laser Infrared Molecular Spectrometer: Instrument Development for Chemical Sensing
The ability to observe and identify the presence of trace gases within an environment is a paramount capability needed to advance earth and planetary atmospheric research. Detection of trace levels of gases is also of interest in defense, industrial, security, medical, and environmental health applications. Current scientific objectives largely focus on identifying the presence of specific gases and isotopologues found in planetary atmospheres within our solar system. The presence and relative amounts of these gases allows scientists to deduce history of the planetary atmosphere and the likelihood that life has or could exist there. One challenge is accurately acquiring the data needed to make reliable conclusions when some of the target gas molecules are present in trace quantities of 10 parts per billion (ppb) or less. Laser gas spectrometers are effective ways of collecting in situ gas measurements, but their precision is directly proportional to the path length of the optical system. The Scanning Laser Infrared Molecular Spectrometer (SLIMS) is a novel solution that achieves very long effective path lengths, which yield ppb and sub-ppb measurements of trace gases. It can also accommodate multiple laser channels covering a wide range of wavelengths resulting in detection of more chemicals of interest. The mechanical design of the mirror cell allows for the large effective path length within a small footprint. The same design provides a robust structure which lends itself to being immune to some of the alignment challenges that similar cells face. The continued forward progress of the SLIMS project will rely on optimizing the optical paths and optical alignment geometries. Missions referred to in this document are for planning and discussion purposes only.
The HITRAN 2008 molecular spectroscopic database
Journal of Quantitative Spectroscopy and Radiative Transfer, 2009
This paper describes the status of the 2008 edition of the HITRAN molecular spectroscopic database. The new edition is the first official public release since the 2004 edition, although a number of crucial updates had been made available online since 2004. The HITRAN compilation consists of several components that serve as input for radiative-transfer calculation codes: individual line parameters for the microwave through visible spectra of molecules in the gas phase; absorption cross-sections for molecules having dense spectral features, i.e., spectra in which the individual lines are not resolved; individual line parameters and absorption crosssections for bands in the ultra-violet; refractive indices of aerosols, tables and files of general properties associated with the database; and database management software. The line-by-line portion of the database contains spectroscopic parameters for forty-two molecules including many of their isotopologues. 3
Evolution of imaging spectrometry: past, present, and future
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An overview of the physical principals of imaging spectrometry for detailed characterization of remote objects and of gas vapors is given. The terms Multi-spectral, Hyperspectral, and Ultra-spectral are defined within the framework of applications and instrument system design approaches. History of the development of imaging spectrometers is reviewed. We are at the threshold of major commercial efforts for these instrument systems.
Pulsed nozzle Fourier transform microwave spectrometer: Ideal to define hydrogen bond radius
2000
A pulsed nozzle Fourier transform microwave (PNFTMW) spectrometer has been recently fabri- cated at the Indian Institute of Science. The basic design is the same as that of Balle and Flygare. How - ever, recent advances in microwave and computer technologies have helped in designing a state -of-the- art PNFTMW spectrometer. The range of the spectro- meter is from 2