ION DIP SPECTROSCOPY OF VANDERWAALS CLUSTERS

We report the implementation of ion dip spectroscopy in a supersonic molecular beam time-of-flight mass spectrometer as a powerful mass-selective method for observing ground-state vibrational levels in van der Waals clusters. Ion dip spectra of phenylacetylene and phenylacetylene-NH3 are demonstrated in the range of 900-1100 cm-1, showing prominent dips at 978.0,1002.8, and 1028.0 cm-1. These dips have been tentatively assigned as 1310 3511, 11 10 3501, and 352 1, respectively, in phenylacetylene. Shifts in the 35 21 and 1110350 1 vibrational bands of the complex are observed while the 13 10 3511 band of the complex is either shifted or attenuated. © 1990 American Institute of Physics.