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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.


Schematic representation of the relevant distances in the experiment (a) together with a schematic representation of the trigger scheme (b) needed to synchronize the experiment. c Arrival time distribution of ND 3 seeded in Kr at the detector, when the beam propagates in free flight from the source to the detector. Time-of-flight (TOF) distribution and Incouple Time Scan (ITS) when this beam is guided at constant speed (d) or decelerated (e). See text for details
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Fig3: Schematic representation of the relevant distances in the experiment (a) together with a schematic representation of the trigger scheme (b) needed to synchronize the experiment. c Arrival time distribution of ND 3 seeded in Kr at the detector, when the beam propagates in free flight from the source to the detector. Time-of-flight (TOF) distribution and Incouple Time Scan (ITS) when this beam is guided at constant speed (d) or decelerated (e). See text for details

Mentions: The relevant distances in the experiment are defined in Fig. 3a, together with a schematic representation of the trigger scheme in the experiment in panel b. The distance between valve orifice and Stark decelerator is denoted by L1, the decelerator itself has length L2, and the distance between exit of the decelerator and interaction region is given by L3. In the most basic trigger scheme, the experiment only involves three timings. We define the trigger pulse to open the valve as t=T0. The first high voltage pulse to the Stark decelerator is then applied at t=Tinc. It is convenient to apply the burst sequence at the time when the synchronous molecule has reached the center of the first electrode pair. We refer to this time as the incoupling time. The Stark decelerator itself is operated by applying a burst of high voltage pulses to the electrodes through a programmable pulse generator. The burst itself is pre-calculated, and cannot (and should not!) be optimized during the experiment. Finally, the laser is fired at time t=Tdetect, leaving a time difference ΔTff between the laser trigger pulse and the time Toff at which the last high voltage pulse of the decelerator is switched off. During this time, the molecules propagate in free flight with the final velocity that was obtained in the last stage of the decelerator.Fig. 3


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

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

Schematic representation of the relevant distances in the experiment (a) together with a schematic representation of the trigger scheme (b) needed to synchronize the experiment. c Arrival time distribution of ND 3 seeded in Kr at the detector, when the beam propagates in free flight from the source to the detector. Time-of-flight (TOF) distribution and Incouple Time Scan (ITS) when this beam is guided at constant speed (d) or decelerated (e). See text for details
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig3: Schematic representation of the relevant distances in the experiment (a) together with a schematic representation of the trigger scheme (b) needed to synchronize the experiment. c Arrival time distribution of ND 3 seeded in Kr at the detector, when the beam propagates in free flight from the source to the detector. Time-of-flight (TOF) distribution and Incouple Time Scan (ITS) when this beam is guided at constant speed (d) or decelerated (e). See text for details
Mentions: The relevant distances in the experiment are defined in Fig. 3a, together with a schematic representation of the trigger scheme in the experiment in panel b. The distance between valve orifice and Stark decelerator is denoted by L1, the decelerator itself has length L2, and the distance between exit of the decelerator and interaction region is given by L3. In the most basic trigger scheme, the experiment only involves three timings. We define the trigger pulse to open the valve as t=T0. The first high voltage pulse to the Stark decelerator is then applied at t=Tinc. It is convenient to apply the burst sequence at the time when the synchronous molecule has reached the center of the first electrode pair. We refer to this time as the incoupling time. The Stark decelerator itself is operated by applying a burst of high voltage pulses to the electrodes through a programmable pulse generator. The burst itself is pre-calculated, and cannot (and should not!) be optimized during the experiment. Finally, the laser is fired at time t=Tdetect, leaving a time difference ΔTff between the laser trigger pulse and the time Toff at which the last high voltage pulse of the decelerator is switched off. During this time, the molecules propagate in free flight with the final velocity that was obtained in the last stage of the decelerator.Fig. 3

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.