The chemistry of AlF and CaF production in buffer gas sources.

In this work, we explore the role of chemical reactions on the properties of buffer gas cooled molecular beams. In particular, we focus on scenarios relevant to the formation of AlF and CaF via chemical reactions between the Ca and Al atoms ablated from a solid target in an atmosphere of a fluorine-containing gas, in this case, SF and NF. Reactions are studied following an ab initio molecular dynamics approach, and the results are rationalized following a tree-shaped reaction model based on Bayesian inference.

Spectroscopic characterization of singlet-triplet doorway states of aluminum monofluoride.

Aluminum monofluoride (AlF) possesses highly favorable properties for laser cooling, both via the AΠ and aΠ states. Determining efficient pathways between the singlet and the triplet manifold of electronic states will be advantageous for future experiments at ultralow temperatures. The lowest rotational levels of the AΠ, v = 6 and bΣ, v = 5 states of AlF are nearly iso-energetic and interact via spin-orbit coupling.

Hyperfine-resolved optical spectroscopy of the AΠ ← XΣ transition in MgF.

We report on hyperfine-resolved laser spectroscopy of the AΠ ← XΣ transition of magnesium monofluoride (MgF), relevant for laser cooling. We recorded 25 rotational transitions with an absolute accuracy of better than 20 MHz, assigned 56 hyperfine lines, and determined precise rotational, fine, and hyperfine structure parameters for the AΠ state. The radiative lifetime of the AΠ state was determined to be 7.

Spectroscopic characterization of the aΠ state of aluminum monofluoride.

Spectroscopic studies of aluminum monofluoride (AlF) have revealed its highly favorable properties for direct laser cooling. All Q lines of the strong AΠ ← XΣ transition around 227 nm are rotationally closed and thereby suitable for the main cooling cycle. The same holds for the narrow, spin-forbidden aΠ ← XΣ transition around 367 nm, which has a recoil limit in the µK range.

The diatomic molecular spectroscopy database.

Motivation: The spectroscopy of diatomic molecules is an important research area in chemical physics due to its relevance in astrochemistry, combustion chemistry, and ultracold physics. However, there is currently no database where the user can easily retrieve, in a useful format, the spectroscopic constants of a given molecule. A similar situation appears concerning the vibrational Franck-Condon factors for diatomic molecules, a crucial parameter to infer laser cooling prospects for molecules.

Magnetic Trapping and Coherent Control of Laser-Cooled Molecules.

We demonstrate coherent microwave control of the rotational, hyperfine, and Zeeman states of ultracold CaF molecules, and the magnetic trapping of these molecules in a single, selectable quantum state. We trap about 5×10^{3} molecules for almost 2 s at a temperature of 70(8)  μK and a density of 1.2×10^{5}  cm^{-3}.

A search for varying fundamental constants using hertz-level frequency measurements of cold CH molecules.

Many modern theories predict that the fundamental constants depend on time, position or the local density of matter. Here we develop a spectroscopic method for pulsed beams of cold molecules, and use it to measure the frequencies of microwave transitions in CH with accuracy down to 3 Hz. By comparing these frequencies with those measured from sources of CH in the Milky Way, we test the hypothesis that fundamental constants may differ between the high- and low-density environments of the Earth and the interstellar medium.

Wave and particle in molecular interference lithography.

The wave-particle duality of massive objects is a cornerstone of quantum physics and a key property of many modern tools such as electron microscopy, neutron diffraction or atom interferometry. Here we report on the first experimental demonstration of quantum interference lithography with complex molecules. Molecular matter-wave interference patterns are deposited onto a reconstructed Si(111) 7x7 surface and imaged using scanning tunneling microscopy.