文档介绍：CHAPTER 9 Microwave Spectroscopy Reporter: liu ping Applications Before outlining the applications of microwave spectroscopy, it will be useful to review the conditions that must be satisfied in order to observe and characterize microwave spectra. Many weakly pounds with small moments give only weak microwave absorption peaks. When using instruments with higher sensitivity (higher signal-to-noise ratio), we can detect such weakly polar hydrocarbons as propylene, isobutene, and propane which have already been studied in considerable detai l. The first requirement is that the substance to be analyzed have a permanent electric dipole moment. pounds of low volatility can be analyzed using heated cells. Cells have been constructed for use at temperatures as high as 1000 ? C, but at present they are very inconvenient to use. As high-temperature cells mercially available, the applications of microwave spectroscopy should greatly expand. Second, the sample should be in the form of a gas, and 50 to 100 μ m vapor pressure is typically required. Despite these requirements and limitations there are a large number of molecules whose microwave spectra can be conveniently measured. The applications of such spectra are mainly for qualitative and quantitative analysis and structure elucidation. Qualitative analysis 1. An excellent technique for qualitative identification of pounds . 2. The microwave spectrum is a property of the molecule as a whole, giving a unique fingerprint for the molecule. 3. Absorption lines are very sharp and readily resolved with the instruments available. 4. The information-handing capacity of the microwave region is extremely high . If we consider the readily accessible range of, say, 10 to 50 GHz, and take a typical line width of MHz (10 -4 GHz), there is space in the spectrum for 400,000 lines. This means that it should be possible, in principle