Speaker
Description
Over the past 15 years, the development of hybrid trapping experiments for cold atoms and ions has enabled a variety of new research directions and applications in the realm of atomic, molecular and chemical physics [1]. We introduce here an extension of this approach to the molecular domain by combining an ion trap and a molecular trap as a new way to explore low-temperature ion-molecule collisions.
We present an experimental realization of a hybrid trap for OH molecules and Ca$^+$ ions, with the potential to implement other molecular ions through sympathetic cooling. A supersonic beam of OH radicals is decelerated using a Stark decelerator and loaded into a magnetic trap formed by permanent magnets [2]. The Ca$^+$ ions are initially trapped and Doppler cooled in one stage of a segmented linear Paul trap and then transported to be overlapped with the trapped OH molecules.
Once superimposed, strong magnetic field gradients from the OH trap induce position-dependent Zeeman shifts on the Ca$^+$ ions disrupting laser cooling. This is mitigated using two cooling lasers with precisely tuned wavelengths and polarizations, along with a repumping laser, enabling efficient cooling to millikelvin temperatures comparable to field-free conditions [3,4].
With the successful realization of the hybrid trap, cold collisions between OH molecules and Ca$^+$ ions are being investigated in our lab. First experimental results will be presented, along with a novel method for determining the number and temperature of Coulomb-crystallized ions using convolutional neural networks [5].
[1] M. Deiß, S. Willitsch and J. H. Denschlag, Nat. Phys. 20, 713 (2024)
[2] D. Haas, C. von Planta, T. Kierspel, D. Zhang, and S. Willitsch. Commun. Phys. 2(1), 101 (2019)
[3] R. Karl, Y. Yin, and S. Willitsch. Mol. Phys. 2199099 (2023)
[4] C. Mangeng, Y. Yin, R. Karl, and S. Willitsch. Phys. Rev. Research 5(4), 043180 (2023)
[5] Y. Yin, and S. Willitsch. arXiv:2502.18442 (2025)
