Description:A detailed and rigorous presentation of the spectroscopy and dynamics of orientationally structured adsorbates. It is intended largely for specialists and graduate students in solid state theory and surface physics. To make the volume readable also for beginners in surface science, a lucid style is used and many references on orientational surface structures and vibrational excitations in them is offered. The text is supplemented with two indices (alphabetical listing of subjects and authors, as well as cross-references) which should enable the reader to easily access the information both on principal concepts involved and on specific adsorbate compositions.