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Topic Name: The HITRAN 2004 molecular spectroscopic database : Matter in the gas phase interacts

Category: Aeronautical

Research persons: Dr. Laurence S. RothmanPhysicist
Harvard-Smithsonian Center for Astrophysics
Atomic and Molecular Physics Division

Location: Cambridge, MA, USA, United States

Details

This paper describes the status of the 2004 edition of the HITRAN molecular spectroscopic database. 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 unresolvable; individual line parameters and absorption cross-sections 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 39 molecules including many of their isotopologues. The format of the section of the database on individual line parameters of HITRAN has undergone the most extensive enhancement in almost two decades. It now lists the Einstein A-coefficients, statistical weights of the upper and lower levels of the transitions, a better system for the representation of quantum identifications, and enhanced referencing and uncertainty codes. In addition, there is a provision for making corrections to the broadening of line transitions due to line mixing.
Laurence S. Rothman answers a few questions about this month's new hot paper in the field of Engineering.

Why do you think your paper is highly cited?
The HITRAN spectroscopic database which I manage provides input for a vast array of applications in the scientific, industrial, and academic community. I currently maintain a list of about 5,500 active users throughout the world.
Does it describe a new discovery or a new methodology that's useful to others?
HITRAN is an archive of spectroscopic data that has been cast into a convenient format for general use. It is continuously enhanced with new data acquired from recent experiments and theoretical calculations, and they have been validated for inclusion into the database.
Could you summarize the significance of your paper in layman's terms?
Matter in the gas phase interacts with electromagnetic radiation such as visible light, infrared, microwave, and ultraviolet. Due to the physics of quantum mechanics, the molecules absorb the radiation at discrete frequencies. This so-called spectrum resembles a set of uneven picket fences, and is unique to each molecule. In essence, each species has its own special "fingerprint." Owing to the high sensitivity and resolution of modern instruments, one is able to extract a great deal of information about the scene if one has the spectroscopic "template" of the species in question. The HITRAN database provides such an archive for many gases, and enables scientists to obtain information such as the quantity of gas in the path, the temperature of the gas, or the pressure, without physically interfering with the gas being probed. HITRAN acts as an analogy to the human genome project.
How did you become involved in this research, and were any problems encountered along the way?
My doctoral studies were in obtaining highly accurate energy levels and intensities of molecules like water vapor, ozone, and sulfur dioxide, by using theoretical methods. At about that time, a confluence of technologies became available: computational power, sensitive detectors, and new high-resolution spectrometers. These technologies led to the need for a machine-readable compilation of spectroscopic parameters. The ensuing problems have been in keeping up with the demands of observations, particularly the improved satellite remote-sensing experiments, which are requiring very high accuracy of the spectroscopic parameters. In addition, the increased sophistication of remote-sensing retrieval algorithms has made necessary the inclusion of more subtle physical effects in the database. Funding the effort of such a scale has also been a continual challenge.
What are the social or political implications of your research?
HITRAN is unique in many ways. It includes information about a wide array of atmospheric molecules and is invaluable in many applications. A stringent testing of the data, before inclusion into the archive, makes it a worldwide standard for much smaller and highly specialized databases. It is also an international effort, involving scientific research from many well-established research laboratories. There are many implications of the research to which HITRAN is applied. It is used extensively for monitoring of the terrestrial atmosphere, especially global warming, ozone depletion, and trace-gas (atmospheric pollutant) change. These have an effect on government policies. The commercial uses, such as detecting pollution, monitoring industrial processes and effluents, and surveillance are very extensive. The database has many military applications, especially in the detection of plumes seen through the atmosphere in order to provide advanced warnings on the launching of missiles. The HITRAN database also has applications with regard to astronomy and astrophysics. Examples are provided in a recent session on "Spectroscopy and Radiative Transfer in Planetary Atmospheres" that was held at the European Geosciences Union conference in Vienna. Indeed, the database applications for extra-solar planets, stars, and eventually astrobiology, are very exciting prospects for the future.

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