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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.


Related in: MedlinePlus

Experimental (red curves) and simulated (blue curves) TOF profiles for ND 3 molecules exiting the Stark decelerator, when a Jordan Valve (left column) or a Nijmegen Pulsed Valve (right column) is used. The Stark decelerator is operated to decelerate (ϕ0>0°) a packet of molecules, and Kr (panel a - d) or Xe (panel e - h) is used as seed gas. The selected velocity from the molecular beam pulse, the phase angle ϕ0 that is used in the decelerator, as well as the velocity with which the packet exits the decelerator, is indicated in each panel. Peak intensities are normalized. The Jordan Valve is approximately three times less intense compared to the Nijmegen Pulsed Valve. Note that the Nijmegen Pulsed Valve allows for deceleration to lower final velocities for identical phase angles and carrier gases compared to the Jordan Valve
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Fig6: Experimental (red curves) and simulated (blue curves) TOF profiles for ND 3 molecules exiting the Stark decelerator, when a Jordan Valve (left column) or a Nijmegen Pulsed Valve (right column) is used. The Stark decelerator is operated to decelerate (ϕ0>0°) a packet of molecules, and Kr (panel a - d) or Xe (panel e - h) is used as seed gas. The selected velocity from the molecular beam pulse, the phase angle ϕ0 that is used in the decelerator, as well as the velocity with which the packet exits the decelerator, is indicated in each panel. Peak intensities are normalized. The Jordan Valve is approximately three times less intense compared to the Nijmegen Pulsed Valve. Note that the Nijmegen Pulsed Valve allows for deceleration to lower final velocities for identical phase angles and carrier gases compared to the Jordan Valve

Mentions: The TOFs pertaining to deceleration using Kr and Xe as a carrier gas, and using the phase angles 50° and 70°, are shown in Fig. 6. It is noted that when an NPV and Xe are used, a final velocity of 154 m/s is reached when ϕ0=54°. This is the lowest final velocity obtainable in the s=3 mode of operation [41], and deceleration to lower final velocities is beyond the scope of the studies presented here. In all TOFs, the decelerated bunch of molecules is separated from the remainder of the gas pulse, and its signature is clearly visible. Interesting broad and narrow oscillatory structures are visible in the TOFs of the non-decelerated parts of the beam. These structures have been observed and interpreted before in Stark-deceleration experiments using the OH radical [35, 36].Fig. 6


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

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

Experimental (red curves) and simulated (blue curves) TOF profiles for ND 3 molecules exiting the Stark decelerator, when a Jordan Valve (left column) or a Nijmegen Pulsed Valve (right column) is used. The Stark decelerator is operated to decelerate (ϕ0>0°) a packet of molecules, and Kr (panel a - d) or Xe (panel e - h) is used as seed gas. The selected velocity from the molecular beam pulse, the phase angle ϕ0 that is used in the decelerator, as well as the velocity with which the packet exits the decelerator, is indicated in each panel. Peak intensities are normalized. The Jordan Valve is approximately three times less intense compared to the Nijmegen Pulsed Valve. Note that the Nijmegen Pulsed Valve allows for deceleration to lower final velocities for identical phase angles and carrier gases compared to the Jordan Valve
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig6: Experimental (red curves) and simulated (blue curves) TOF profiles for ND 3 molecules exiting the Stark decelerator, when a Jordan Valve (left column) or a Nijmegen Pulsed Valve (right column) is used. The Stark decelerator is operated to decelerate (ϕ0>0°) a packet of molecules, and Kr (panel a - d) or Xe (panel e - h) is used as seed gas. The selected velocity from the molecular beam pulse, the phase angle ϕ0 that is used in the decelerator, as well as the velocity with which the packet exits the decelerator, is indicated in each panel. Peak intensities are normalized. The Jordan Valve is approximately three times less intense compared to the Nijmegen Pulsed Valve. Note that the Nijmegen Pulsed Valve allows for deceleration to lower final velocities for identical phase angles and carrier gases compared to the Jordan Valve
Mentions: The TOFs pertaining to deceleration using Kr and Xe as a carrier gas, and using the phase angles 50° and 70°, are shown in Fig. 6. It is noted that when an NPV and Xe are used, a final velocity of 154 m/s is reached when ϕ0=54°. This is the lowest final velocity obtainable in the s=3 mode of operation [41], and deceleration to lower final velocities is beyond the scope of the studies presented here. In all TOFs, the decelerated bunch of molecules is separated from the remainder of the gas pulse, and its signature is clearly visible. Interesting broad and narrow oscillatory structures are visible in the TOFs of the non-decelerated parts of the beam. These structures have been observed and interpreted before in Stark-deceleration experiments using the OH radical [35, 36].Fig. 6

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.


Related in: MedlinePlus