Published: Jan 2002
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IN THE PREVIOUS CHAPTER, the nature of radiation in certain portions of the electromagnetic spectrum was discussed. As was seen, radiation is composed of wave packets called photons with characteristic and discrete energy levels. The radiation associated with ultraviolet curing or photocuring is known as “nonionizing” or “actinic” radiation. It is radiation that usually does not produce electrically charged particles, free electrons, or ions, and it is electromagnetic energy that is capable of producing photochemical activity. Photons with sufficient energy can produce electrons; however, in photocuring such photons are not usually available. Radiation that is associated with electron beam curing is “ionizing” radiation, and it is energy that can directly or indirectly form ions and generate electrons while traveling through a substance. Other energy sources used today include lasers and light or visible radiation. Although these latter sources are not broadly used in commerce today, they may well be of future importance and will be briefly discussed at the end of this chapter.