By Jim Nolen
Introduction-- An Historical Perspective:
Who would have guessed one
hundred and fifty years ago that things so ordinary as light and color might unlock
countless mysteries of the atom? In 1885, before the dawn of quantum mechanics,
Johann Balmer developed a simple formula which accurately described the four lowest
emission lines of the hydrogen atom (Serway 1202). Other similar formulas describing
the emission of light from hydrogen were developed shortly thereafter: the Lyman series,
the Paschen series, and the Brackett series (Serway 1202). Despite the acuracy of
such observations, classical physics could do nothing to explain the dynamics of this
close relationship between light and atoms. At the dawn of the twentieth century, a
new era of physics dawned as well. In 1900, German physicist Max Planck determined a
very accurate formula to predict the thermal radiation emitted from a so-called
"black body" (Serway 1192). Furthermore, he reasoned that electromagnetic
energy existed in discreet amounts proportional to a constant which became known as
Planck's constant (Sandin 73). Five years later in his Nobel Prize winning paper on
the photoelectric effect , Albert Einstein provided a crucial link between this
quantization of electromagentic energy and the ionization of atoms (Serway 1194).
These and several other developments (such as the Schodinger equation and the construction
of the laser) led the development of modern spectroscopic techniques: using light to probe
the energy levels of the atom and of molecules.
These pages discuss a few modern
spectroscopic techniques and demonstrate their usefulness in describing molecular
dynamics, atomic energy levels, and quantum mechanical concepts. The discussion
begins with molecular spectroscopy and the dynamics of the CO2 molecule and CO2
laser. The next section is an explanation of two-photon absorption and three-photon
ionization as seen in Cesium atoms. Finally, Raman Spectroscopy is discussed as it
relates to four-wave mixing in Sodium vapor. Each of the experiments described were
conducted under the guidance of Dr. Wolfgang Christian in the spring of 1999 for
Intermediate Laboratory, Davidson College Department of Physics. Derek Kverno also
participated in the development and analysis of these experiments.
Table of Contents:
- Andrews, David L. Applied Laser Spectroscopy. New York, VCH
- Demtröder, Wolfgang. Laser Spectroscopy. New York: Springer, 1996.
- Eastham, Derek. Atomic Physics of Lasers. Philadelphia: Taylor and
- Eberly, Joseph H. and Peter W. Milonni. Lasers. New York: John Wiley
and Sons, 1988.
- Hazel, T.P, et.al. "Classical View of the Properties of Rydberg Atoms: Application
of the Correspondence Principle." American Journal of Physics. Vol
60. No. 4. April 1992. pp 329-335.
- Measures, R. M. "Analytical Use of Lasers in Remote Sensing." Analytical
Laser Spectroscopy. Nicolo Omenetto, ed. New York: John Wiley and Sons,
1979. pp 295-410.
- Moore, Charlotte E. Atomic Energy Levels. Vol II. U.S. Department of
Commerce. National Bureau of Standards. December, 1971.
- Moore, Mary Anne Kozilsky. The Nonlinear Optical Response of Sodium Vapor When Pumped to a Two-Photon Resonance.
Ph.D. Dissertation. University of Tennessee, Knoxville. August 1988.
- Sandin, T.R. Essentials of Modern Physics. New York: Addison-Wesley, 1989.
- Serway, Raymond A. Physics For Scientists and Engineers. Philadelphia:
Saunders College Publishing, 1996.
- Shankland, Robert S. Atomic and Nuclear Physics. New York: MacMillan
- Zumdahl, Steven S. Chemical Principles. Lexington: D.C. Heath and Company,