We demonstrate the spatial separation of pyrrole and pyrrole(H 2 O) clusters from the other atomic and molecular species in a supersonically-expanded beam of pyrrole and traces of water seeded in high-pressure helium gas. The experimental results are quantitatively supported by simulations. The obtained pyrrole(H 2 O) cluster beam has a purity of ∼100 %. The extracted rotational temperature of pyrrole and pyrrole(H 2 O) from the original supersonic expansion is T rot = 0.8 ± 0.2 K, whereas the temperature of the deflected, pure-pyrrole(H 2 O) part of the molecular beam corresponds to T rot ≈ 0.4 K.

A knife edge for shaping a molecular beam is described to improve the spatial separation of the species in a molecular beam by the electrostatic deflector. The spatial separation of different molecular species from each other as well as from atomic seed gas is improved. The column density of the selected molecular-beam part in the interaction zone, which corresponds to higher signal rates, was enhanced by a factor of 1.5, limited by the virtual source size of the molecular beam.