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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 experimental set-up. A pulsed beam of ND 3 or NO molecules seeded in Ar, Kr or Xe is produced by either a Jordan Valve or a Nijmegen Pulsed Valve and loaded into the Stark decelerator. After passing through this 2.6 meter-long Stark decelerator, of which only the last section is shown, the molecules are detected in the interaction region using Resonance Enhanced Multi Photon Ionization (REMPI). A one-color (2+1) or a two-color (1+1’) REMPI scheme is used to detect ND 3 or NO, respectively. The microchannel plate detector can either be used to record the integral ion signal, or to record the velocity of the molecules using VMI. Molecular beams produced by a Jordan Valve and a Nijmegen Pulsed Valve are available at an angle of 90° and 180° with respect to the Stark decelerator, respectively. Both beams are collimated by a skimmer (s) and a collimator (c). These beams allow for scattering experiments, but in this study they are used to characterize the velocity distribution of the conventional beams
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Fig1: Schematic representation of the experimental set-up. A pulsed beam of ND 3 or NO molecules seeded in Ar, Kr or Xe is produced by either a Jordan Valve or a Nijmegen Pulsed Valve and loaded into the Stark decelerator. After passing through this 2.6 meter-long Stark decelerator, of which only the last section is shown, the molecules are detected in the interaction region using Resonance Enhanced Multi Photon Ionization (REMPI). A one-color (2+1) or a two-color (1+1’) REMPI scheme is used to detect ND 3 or NO, respectively. The microchannel plate detector can either be used to record the integral ion signal, or to record the velocity of the molecules using VMI. Molecular beams produced by a Jordan Valve and a Nijmegen Pulsed Valve are available at an angle of 90° and 180° with respect to the Stark decelerator, respectively. Both beams are collimated by a skimmer (s) and a collimator (c). These beams allow for scattering experiments, but in this study they are used to characterize the velocity distribution of the conventional beams

Mentions: The experiments were performed in a molecular beam machine that is optimized for high-resolution crossed beam scattering experiments. It consists of a 2.6 meter-long Stark decelerator, two conventional molecular beams that are positioned at an angle of 90° and 180° with respect to the Stark decelerator’s axis, and a velocity map imaging (VMI) detector. This apparatus is schematically shown in Fig. 1, and has been described in detail elsewhere [33]. We here only describe the parts that are most relevant for the studies presented here.Fig. 1


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 experimental set-up. A pulsed beam of ND 3 or NO molecules seeded in Ar, Kr or Xe is produced by either a Jordan Valve or a Nijmegen Pulsed Valve and loaded into the Stark decelerator. After passing through this 2.6 meter-long Stark decelerator, of which only the last section is shown, the molecules are detected in the interaction region using Resonance Enhanced Multi Photon Ionization (REMPI). A one-color (2+1) or a two-color (1+1’) REMPI scheme is used to detect ND 3 or NO, respectively. The microchannel plate detector can either be used to record the integral ion signal, or to record the velocity of the molecules using VMI. Molecular beams produced by a Jordan Valve and a Nijmegen Pulsed Valve are available at an angle of 90° and 180° with respect to the Stark decelerator, respectively. Both beams are collimated by a skimmer (s) and a collimator (c). These beams allow for scattering experiments, but in this study they are used to characterize the velocity distribution of the conventional beams
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig1: Schematic representation of the experimental set-up. A pulsed beam of ND 3 or NO molecules seeded in Ar, Kr or Xe is produced by either a Jordan Valve or a Nijmegen Pulsed Valve and loaded into the Stark decelerator. After passing through this 2.6 meter-long Stark decelerator, of which only the last section is shown, the molecules are detected in the interaction region using Resonance Enhanced Multi Photon Ionization (REMPI). A one-color (2+1) or a two-color (1+1’) REMPI scheme is used to detect ND 3 or NO, respectively. The microchannel plate detector can either be used to record the integral ion signal, or to record the velocity of the molecules using VMI. Molecular beams produced by a Jordan Valve and a Nijmegen Pulsed Valve are available at an angle of 90° and 180° with respect to the Stark decelerator, respectively. Both beams are collimated by a skimmer (s) and a collimator (c). These beams allow for scattering experiments, but in this study they are used to characterize the velocity distribution of the conventional beams
Mentions: The experiments were performed in a molecular beam machine that is optimized for high-resolution crossed beam scattering experiments. It consists of a 2.6 meter-long Stark decelerator, two conventional molecular beams that are positioned at an angle of 90° and 180° with respect to the Stark decelerator’s axis, and a velocity map imaging (VMI) detector. This apparatus is schematically shown in Fig. 1, and has been described in detail elsewhere [33]. We here only describe the parts that are most relevant for the studies presented here.Fig. 1

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.