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Optimal beam sources for Stark decelerators in collision experiments: a tutorial review.

Vogels SN, Gao Z, van de Meerakker SY - EPJ Tech Instrum (2015)

Bottom Line: The performance of two valves in particular, the Nijmegen Pulsed Valve and the Jordan Valve, is illustrated by decelerating ND 3 molecules in a 2.6 meter-long Stark decelerator.We describe a protocol to characterize the valve, and to optimally load the pulse of molecules into the decelerator.We characterize the valves regarding opening time duration, optimal valve-to-skimmer distance, mean velocity, velocity spread, state purity, and relative intensity.

View Article: PubMed Central - PubMed

Affiliation: Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, AJ Nijmegen, 6525 Netherlands.

ABSTRACT

With the Stark deceleration technique, packets of molecules with a tunable velocity, a narrow velocity spread, and a high state purity can be produced. These tamed molecular beams find applications in high resolution spectroscopy, cold molecule trapping, and controlled scattering experiments. The quality and purity of the packets of molecules emerging from the decelerator critically depend on the specifications of the decelerator, but also on the characteristics of the molecular beam pulse with which the decelerator is loaded. We consider three frequently used molecular beam sources, and discuss their suitability for molecular beam deceleration experiments, in particular with the application in crossed beam scattering in mind. The performance of two valves in particular, the Nijmegen Pulsed Valve and the Jordan Valve, is illustrated by decelerating ND 3 molecules in a 2.6 meter-long Stark decelerator. We describe a protocol to characterize the valve, and to optimally load the pulse of molecules into the decelerator. We characterize the valves regarding opening time duration, optimal valve-to-skimmer distance, mean velocity, velocity spread, state purity, and relative intensity.

No MeSH data available.


Longitudinal phase-space acceptance (white curve) of the Stark decelerator for ϕ0=0°, together with a schematic representation of the phase-space area of the molecular beam pulse at the entrance of the Stark decelerator for a Nijmegen Pulsed Valve (a) and a Jordan Valve (b)
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Fig7: Longitudinal phase-space acceptance (white curve) of the Stark decelerator for ϕ0=0°, together with a schematic representation of the phase-space area of the molecular beam pulse at the entrance of the Stark decelerator for a Nijmegen Pulsed Valve (a) and a Jordan Valve (b)

Mentions: This valve opening behavior has large consequences on the operation of Stark decelerators. Referring back to Fig. 2, the Stark decelerator selects the part of the molecular beam pulse that overlaps with the first bucket of the decelerator. In Fig. 7 the phase-space distribution of the molecular beam at the entrance of the decelerator is schematically shown for both valves. The relatively constant mean speed of the beam during the valve opening pulse for the NPV results in a phase-space distribution with a position spread that is approximately given by v0τ. For Ar, Kr and Xe seeded beams this results in a spatial width of about 12, 9 and 7 mm, respectively, which is indeed smaller than the spatial dimensions of the decelerator bucket.Fig. 7


Optimal beam sources for Stark decelerators in collision experiments: a tutorial review.

Vogels SN, Gao Z, van de Meerakker SY - EPJ Tech Instrum (2015)

Longitudinal phase-space acceptance (white curve) of the Stark decelerator for ϕ0=0°, together with a schematic representation of the phase-space area of the molecular beam pulse at the entrance of the Stark decelerator for a Nijmegen Pulsed Valve (a) and a Jordan Valve (b)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4527007&req=5

Fig7: Longitudinal phase-space acceptance (white curve) of the Stark decelerator for ϕ0=0°, together with a schematic representation of the phase-space area of the molecular beam pulse at the entrance of the Stark decelerator for a Nijmegen Pulsed Valve (a) and a Jordan Valve (b)
Mentions: This valve opening behavior has large consequences on the operation of Stark decelerators. Referring back to Fig. 2, the Stark decelerator selects the part of the molecular beam pulse that overlaps with the first bucket of the decelerator. In Fig. 7 the phase-space distribution of the molecular beam at the entrance of the decelerator is schematically shown for both valves. The relatively constant mean speed of the beam during the valve opening pulse for the NPV results in a phase-space distribution with a position spread that is approximately given by v0τ. For Ar, Kr and Xe seeded beams this results in a spatial width of about 12, 9 and 7 mm, respectively, which is indeed smaller than the spatial dimensions of the decelerator bucket.Fig. 7

Bottom Line: The performance of two valves in particular, the Nijmegen Pulsed Valve and the Jordan Valve, is illustrated by decelerating ND 3 molecules in a 2.6 meter-long Stark decelerator.We describe a protocol to characterize the valve, and to optimally load the pulse of molecules into the decelerator.We characterize the valves regarding opening time duration, optimal valve-to-skimmer distance, mean velocity, velocity spread, state purity, and relative intensity.

View Article: PubMed Central - PubMed

Affiliation: Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, AJ Nijmegen, 6525 Netherlands.

ABSTRACT

With the Stark deceleration technique, packets of molecules with a tunable velocity, a narrow velocity spread, and a high state purity can be produced. These tamed molecular beams find applications in high resolution spectroscopy, cold molecule trapping, and controlled scattering experiments. The quality and purity of the packets of molecules emerging from the decelerator critically depend on the specifications of the decelerator, but also on the characteristics of the molecular beam pulse with which the decelerator is loaded. We consider three frequently used molecular beam sources, and discuss their suitability for molecular beam deceleration experiments, in particular with the application in crossed beam scattering in mind. The performance of two valves in particular, the Nijmegen Pulsed Valve and the Jordan Valve, is illustrated by decelerating ND 3 molecules in a 2.6 meter-long Stark decelerator. We describe a protocol to characterize the valve, and to optimally load the pulse of molecules into the decelerator. We characterize the valves regarding opening time duration, optimal valve-to-skimmer distance, mean velocity, velocity spread, state purity, and relative intensity.

No MeSH data available.