The Basics of Spectroscopy

Excerpt

1.1 Introduction

Spectroscopy is the study of matter using electromagnetic radiation. While this definition is nominally correct, it is rather simple. On this basis, one could argue that everything we know about the universe comes from spectroscopy, since much of we have learned comes from what we see in the world around us. But simply looking at a picture or painting is not usually considered “spectroscopy,” even though the action might involve studying a piece of matter in broad daylight.

While we will not attempt to develop a more detailed definition of spectroscopy in the remainder of this book, we will be examining various aspects of spectroscopy that make it a scientific tool. In order to set the stage better for the various topics that will be presented, we present a quick history of the development of topics relevant to spectroscopy. There are three major topics: matter, light, and the fusion of matter and light that was ultimately (and properly) labeled “spectroscopy.”

1.2 Matter

Throughout most of history, matter was assumed to be continuous—that is, you could separate it into increasingly smaller pieces, and each piece could then be cut into smaller and smaller parts, ad infinitum. Common experience shows that to be the case, doesn't it? Furthermore, ancient philosophers (as thinkers were known at the time) divided matter into several fundamental substances that were subject to various mystical forces. The four fundamental substances, or elements—fire, air, water, and earth—had accompanying attributes—wet, dry, cold, and hot—that they imparted to matter, depending on the relative amounts in each object. Such a description of matter is attributed to the fifth-century B.C. philosopher Empedocles. Figure 1.1 shows the relationship between the four elements and their attributes. Plato and his pupil Aristotle (fifth to fourth century B.C.) supported these ideas and refined them (in part by introducing a fifth “heavenly” element, the ether). Because of Plato's and Aristotle's influence on the thinking of the time (and times since), the “four elements” idea of matter was the prevailing view for centuries in the Western world. (Three additional medical principles—sulfur, salt, and mercury—were added to the repertoire by the sixteenth-century physician Paracelsus.)