On May 15-18, 1961, the 12th Annual Symposium on Spectros copy was held in Chicago. Over the twelve-year history of this meeting, it has continually grown and now ranks as one of the major technical meetings in the field of spectroscopy. The scope of the program itself represents a balance between research applications and control applications, between applied and the more fundamental aspects of spectroscopy. Papers are presented each year in the specialty areas of X -ray, ultraviolet, visible, infrared, Raman, EPR, and NMR spectroscopy. In many instances over the years, excellent work has been re ported at this symposium and no further publication was made. These reports were then essentially lost for further reference. It is the purpose of this publication to provide a source of reference for the papers presented at the 12th Annual Symposium. This first attempt at publishing a proceedings does not include the entire program. Several papers could not be given company clear ance for publication, and several more were intended for verbal presentation only and were never written for publication. I, as Coordinator of the Symposium, would like to express my gratitude to the Symposium Committee, John Ferraro, Elwin Davis, Joseph Ziomek, John Kapetan, L. S. Gray, Jr., Russell J. Hansen, J. A. Sheinkop, L. V. Azaroff, and Carl Moore, whose diligence and labor resulted in a truly fine symposium, and subsequently made pos sible this publication.