CHARACTERIZATION OF ORIENTED MOLECULE BEAMS BY RADIO-FREQUENCY SPECTROSCOPY

Molecular-beam electric-resonance spectroscopy is used to interrogate the rotational states present in a molecular beam of oriented symmetri c-top molecules produced for scattering experiments, Delta M = +/-1 tr ansitions are observed between Stark energy levels in weal; electric f ields and depend on the rotational quantum numbers J and K. Substantia l rotational cooling is apparent in both neat and seeded beams. Each r esonance signal has a complicated dependence upon the high voltage app lied to the hexapole focusing fields because molecules in the newly tr ansformed states have vastly different focusing properties from the or iginal. These effects can be unified using a ''reduced'' focusing volt age that allows intensity comparisons between rotational states, givin g rotational temperatures of 3-4 K for CF3H seeded in He or Ar. Under favorable circumstances, radio frequency ''labeling'' might: allow one to selectively remove one rotational level at a time from an oriented molecular beam and thereby to study the orientation dependence of dif ferent rotational states.