Agilent 5991-3201EN Enhancing Microwave Spectroscopy in Astrophysics Applications - Application Brief c20130 free download

File name 5991-3201EN Enhancing Microwave Spectroscopy in Astrophysics Applications - Application Brief c20130

Enhancing Microwave Spectroscopy in Application Note Astrophysics Applications Overview In popular perception, the vastness of space is an empty vacuum dotted with stars, planets, black holes and other celestial formations. In reality, astrophysicists have shown that space contains low-density matter - gas clouds, dust grains, and more - existing in ionic, atomic or molecular phases. Here on Earth, astrophysicists use techniques such as micro- wave spectroscopy to investigate the chemical composition of the matter that exists within this so called interstellar medium (ISM). Similar to the spectrum analyzers used to characterize the content of wireless communication signals, a spectrometer connected to a radio telescope displays the unique spectra C ho o se the p erfo rmanc e and f or m emitted by the atoms and molecules present in the ISM. In this facto r yo u need : case, the goal is to precisely determine the structure of gas- phase molecules. 8 1 1 8 0 B and M 8 1 9 0 A W i d eb and A rb i trary W avefo rm G enerator The basic approach is to use spectroscopy to create a database of "fingerprints" from known gases and then compare the stored readings to those captured with a spectrometer. In most cases, the process of creating the database can be quite time-consuming. This application brief describes an approach that is faster and more accurate than typical methods. The key element of the solution is an arbitrary waveform generator (AWG) that can provide a fast broadband signal such as a linear frequency sweep or "chirp." Pr ob lem So l uti o n Our application engineering organization worked with a customer to The revised system addresses the root problem in the original enhance a system that includes absorption cells. The medium in the system by eliminating the long, slow sweep of a CW signal at a cells absorbs those parts of the frequency spectrum that resonate series of discrete frequencies. Instead, the system now uses a with the molecules in the sample material; a detector behind the cell high-performance AWG to provide a fast broadband signal that makes the actual measurement. stimulates the full range of frequencies in a matter of microsecond or milliseconds - and then the source is switched off. Because the In the original system, supersonic jets of gas were being stimulated detector sees only the relaxation spectrum emitted by the absorption with a continuous-wave (CW) source. It would typically