Generation of Cold Molecular Beams of CaF and BaF

Jochen Küpper

Aakash Ravi, Loïc Anderegg, Eunmi Chae +10 more

Martin Collignon, Emmanuel Oswald, Marylise Saffre +2 more

We present a compact electrostatic device for producing velocity-controlled bunches of cold molecular ions. In our implementation, BaF molecules are generated in a supersonic expansion and photoionized inside a stack of electrodes providing >99% field homogeneity. Short voltage pulses applied across the structure decelerate the resulting BaF+ ions by several hundred meters per second over only a few millimeters, enabling control of the mean velocity down to the meV regime while preserving a narrow velocity spread. The setup delivers bunches of thousands of ions and thus provides a versatile source for ion-neutral collision studies, high-resolution spectroscopy, and efficient trap loading. Although the present work does not address rovibrational state preparation, threshold photoionization techniques could be straightforwardly combined with this approach to generate ions in a well-defined internal distribution. The instrument, therefore, offers a simple and general route to the controlled preparation of cold molecular ion beams for a broad range of applications in atomic and molecular physics.

Eunmi Chae, Loïc Anderegg, Benjamin L. Augenbraun +7 more

We demonstrate the one-dimensional, transverse magneto-optical compression of a cold beam of calcium monofluoride (CaF). By continually alternating the magnetic field direction and laser polarizations of the magneto-optical trap (RF MOT), a photon scattering rate of is achieved. A 3D model for this RF MOT, validated by agreement with data, predicts a 3D RF MOT capture velocity for CaF of 5 m s –1 .

Sebastiaan Y. T. van de Meerakker, Hendrick L. Bethlem, Gerard Meijer