Alternating-gradient focusing of the benzonitrile-argon van der Waals complex.

We report on the focusing and guiding of the van der Waals complex formed between benzonitrile molecules (C(6)H(5)CN) and argon atoms in a cold molecular beam using an ac electric quadrupole guide. The distribution of quantum states in the guided beam is non-thermal, because the transmission efficiency depends on the state-dependent effective dipole moment in the applied electric fields. At a specific ac frequency, however, the excitation spectrum can be described by a thermal distribution at a rotational temperature of 0.

Producing translationally cold, ground-state CO molecules.

Carbon monoxide molecules in their electronic, vibrational, and rotational ground state are highly attractive for trapping experiments. The optical or ac electric traps that can be envisioned for these molecules will be very shallow, however, with depths in the sub-milliKelvin range. Here, we outline that the required samples of translationally cold CO (X(1)Σ(+), v'' = 0, N'' = 0) molecules can be produced after Stark deceleration of a beam of laser-prepared metastable CO (a(3)Π(1)) molecules followed by optical transfer of the metastable species to the ground state via perturbed levels in the A(1)Π state.

Rotational-state-specific guiding of large molecules.

A beam of polar molecules can be focused and transported through an ac electric quadrupole guide. At a given ac frequency, the transmission of the guide depends on the mass-to-dipole-moment (m/μ) ratio of the molecular quantum state. Here we present a detailed characterization of the m/μ selector, using a pulsed beam of benzonitrile (C(6)H(5)CN) molecules in combination with rotational quantum state resolved detection.