This article tells of a lifelong fascination with light, a messenger bearing
information from realms ranging from the galactic to the submicroscopic.
Personal interactions have shaped and informed this life journey. Accounts
of some of the most important of these are related. Infrared and electronic
spectra have been obtained, often for the first time, for many small free radicals
and molecular ions—short-lived reaction intermediates in most chemical
processes. The infrared spectrum of a molecule tells how its atoms vibrate
with respect to one another and is as characteristic of the molecule as a fingerprint
is of a person. Analysis of this spectrum provides sometimes surprising
information about the structure and chemical bonding of the molecule in its
lowest-energy electronic state. The electronic spectrum provides information
on the molecule in more highly excited electronic states, in which its
structure or reaction pattern may change or it may decompose.