Since the publication in 1950 of Vol. I, Spectra of Diatomic Molecules
of Molecular Spectra and Molecular Structure, much progress has been
made in the field. While there have been some important refinements in
the theory of diatomic molecular spectra, most of the advances have been
in the further exploration of individual spectra. Not only has the
number of molecules about which some spectroscopic data are available
been increased by a factor of 2 to 3, but also the spectroscopic
information about the molecules known in 1950 has been vastly extended.
This is due to the observation of new elec- tronic states (about three
times as many as known before), the enormous improvements in the
accuracy of the constants of the states known in 1950, and the
determination of higher order constants. In view of the increasing use
of spectroscopic information on diatomic molecules in other fields of
physics, in chemistry, and in astrophysics, it appeared desirable to
prepare an up-to-date version of the table of molecular constants in the
appendix of Vol. I. This updating proved to be far more time-consuming
than originally anticipated, and it is only now, 10 years that we are
able to present such a table, which, instead after its initiation, of
the original 80 pages (plus 30 pages of bibliography), now fills a
volume of 700 pages. In the interest of economy, and unlike the original
version, the new table has been produced by photo-offset from the final
manuscript.
