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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.


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Experimental REMPI spectrum of ND 3 molecules exiting the decelerator, probing exclusively the low-field seeking upper component of the inversion doublet for each rotational state. All lines in the spectrum originate from the upper inversion doublet component of the /J,K〉=/1,1〉 state. Population in other rotational states is negligible
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Fig9: Experimental REMPI spectrum of ND 3 molecules exiting the decelerator, probing exclusively the low-field seeking upper component of the inversion doublet for each rotational state. All lines in the spectrum originate from the upper inversion doublet component of the /J,K〉=/1,1〉 state. Population in other rotational states is negligible

Mentions: Another important parameter is the quantum state purity of the packet of molecules emerging from the decelerator. Figure 9 shows a typical REMPI spectrum for ND 3 molecules exiting the decelerator. The optical transition used probes exclusively the low-field seeking upper inversion level of each rotational state [17]. Each line in the spectrum originates from the /J,K〉=/1,1〉 rotational ground state of para-ND 3. No signal at all is detected when probing the high-field seeking lower inversion levels (data not shown), although ionization must then occur in zero ion extraction field to eliminate parity mixing of both inversion doublets. Population in excited rotational states appears negligible, and we conservatively estimate that > 99.5 % of the molecules reside in this state.Fig. 9


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 REMPI spectrum of ND 3 molecules exiting the decelerator, probing exclusively the low-field seeking upper component of the inversion doublet for each rotational state. All lines in the spectrum originate from the upper inversion doublet component of the /J,K〉=/1,1〉 state. Population in other rotational states is negligible
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig9: Experimental REMPI spectrum of ND 3 molecules exiting the decelerator, probing exclusively the low-field seeking upper component of the inversion doublet for each rotational state. All lines in the spectrum originate from the upper inversion doublet component of the /J,K〉=/1,1〉 state. Population in other rotational states is negligible
Mentions: Another important parameter is the quantum state purity of the packet of molecules emerging from the decelerator. Figure 9 shows a typical REMPI spectrum for ND 3 molecules exiting the decelerator. The optical transition used probes exclusively the low-field seeking upper inversion level of each rotational state [17]. Each line in the spectrum originates from the /J,K〉=/1,1〉 rotational ground state of para-ND 3. No signal at all is detected when probing the high-field seeking lower inversion levels (data not shown), although ionization must then occur in zero ion extraction field to eliminate parity mixing of both inversion doublets. Population in excited rotational states appears negligible, and we conservatively estimate that > 99.5 % of the molecules reside in this state.Fig. 9

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