Spectroscopy has an amazing history of development dating
back some 350 years. The initial quest for the solar spectrum
and light dispersion followed by flame spectroscopy, which is
still performed in high school senior grades, already implied
the importance of spectroscopy in physics, chemistry, and
astronomy. The discovery of the hydrogen atom spectrum and
the splitting of spectral lines in the presence of a magnetic
field provided the first testing ground for quantum theory
to be developed soon after. While small molecules became
amenable to electric resonance measurements, the discovery
of nuclear magnetic resonance (NMR) came as a giant leap,
soon adding to the importance of spectroscopy in biology and
medicine. Contemporary development of maser and lasers
toward the second half of the twentieth century has been
instrumental in the advancement of rotational and vibrational
coherence spectroscopy.