Coherence, Interference and Spectra
It is implicitely assumed in all spectroscopy, that the energy distribution in the spectrum of light and other electromagnetic radiation does not change on propagation in free space. This assumption has until fairly recently not been questioned, probably because with light from usual laboratory sources one has never encountered any problem with it. But one should remember that much of traditional spectroscopy — at least in the optical range of the electromagnetic spectrum — has been concerned with radiation from sources which are essentially spatially incoherent. Since the invention of the laser in 1960, spectroscopy of optical radiation from sources which are spatially highly coherent has also been gradually developed; and more recently sources, such as soft x-ray lasers and various synchrotron sources have become available, which are neither spatially completely incoherent, nor fully coherent, i.e. they are partially coherent.
KeywordsSpatial Coherence Source Distribution Angular Separation Source Spectrum Angular Diameter
Unable to display preview. Download preview PDF.