Abstract
A supersonic beam source for SrF and BaF molecules is constructed by combining the expansion of carrier gas (a mixture of 2% SF6 and 98% argon) from an Even-Lavie valve with laser ablation of a barium/strontium metal target at a repetition rate of 10 Hz. Molecular beams with a narrow translational velocity spread are produced at relative values of Δv/v = 0.053(11) and 0.054(9) for SrF and BaF, respectively. The relative velocity spread of the beams produced in our source is lower in comparison with the results from other metal fluoride beams produced in supersonic laser ablation sources. The rotational temperature of BaF is measured to be 3.5 K. The source produces 6 × 108 and 107 molecules per steradian per pulse in the X2Σ+ (ν = 0, N = 1) state of BaF and SrF molecules, respectively, a state amenable to Stark deceleration and laser cooling.
Highlights
A small velocity spread is desirable for highresolution spectroscopy,3–5 for collision experiments,6,7 and for efficient deceleration of molecules in a Stark decelerator
We demonstrate the small velocity spread of the produced beams of SrF and BaF and compare our results with other ablation sources for metal fluorides
They are further sent to a time-to-digital converter (TDC)
Summary
Supersonic expansion is a proven method to produce beams of molecules with a small velocity spread and low translational and rotational temperatures, resulting in relatively high population of the lowest energy states. A small velocity spread is desirable for highresolution spectroscopy, for collision experiments, and for efficient deceleration of molecules in a Stark decelerator. This is because it reduces Doppler broadening, ensures good resolution of the collision energy in collision experiments, and facilitates good phase-space matching at the entrance of the Stark decelerator. Scitation.org/journal/rsi comparison with other valves, which prevents the heating of the gas pulse It can be operated at high backing pressures, which leads to a large pressure gradient, thereby reducing the kinetic temperature of the gas pulse. Such a combination has previously been used to produce beams to study reaction dynamics and collision experiments between atoms and molecules in a magnetic and a static quadrupole trap.. Droplets of helium have been produced by expansion through a pulsed Even–Lavie valve to which lithium atoms are doped by ablation.32 This combination has been used here for the production of supersonic beams of two alkaline-earth metal fluorides, SrF and BaF. These relatively heavy molecules are considered as target probes to test fundamental symmetry violation beyond the Standard Model. We demonstrate the small velocity spread of the produced beams of SrF and BaF and compare our results with other ablation sources for metal fluorides.
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