Neutral cluster mass spectrometry

The application of mass spectrometry (particularly time of flight mass spectrometry - TOFMS) to the study of neutral van der Waals and metal containing covalent clusters is discussed. In order to apply TOFMS to the study of neutral clusters, the clusters are ionized by single photon excitation or by resonance enhanced multiphoton excitation, at or near their ionization thresholds. With these techniques, neutral clusters can be accessed and explored to determine their size, structures, dynamics, reactions, ion chemistry, catalytic behavior, and electronic, vibrational, and rotational energy levels. The histories of specific central cluster species are presented to acquaint the reader with the development of neutral cluster studies since the 1980s. Clearly only the highlights (as we see them) of neutral cluster science can be mentioned and referenced in this overview, the intent of which is to explain the roots of the field, present its evolution, and to proffer at least a few of its continuing, developing directions.