Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

The Journal of Chemical Physics

Pulsed molecular beams: A lower limit on pulse duration for fully developed supersonic expansions

Katherine L. Saenger

Published Sep 1, 1981• 64 citations
Publisher

Abstract

We derive an expression for Δtmin, the mimimum pulse duration (’’valve open time’’) required if a pulsed nozzle is to produce a supersonic beam comparably ’’cold’’ to that obtained from a continuous source.(AIP)
DOI
10.1063/1.442272

Related papers

Design and Characterization of a New Pulsed Molecular-Beam Valve

Ian W Collett

A common technique for producing samples of cold molecules that can be trapped and studied is electromagnetic deceleration of a fast moving, but internally cold, supersonic beam. The quality of these samples, which are ideally as cold and dense as possible, is fundamentally limited by the quality of the beam coupled to the decelerator. This thesis outlines the design, construction, and characterization of a new pulsed valve that produces samples of molecules as short as fifty microseconds.

•Jan 1, 2016•1 citation

Pulsed source of metal atoms and their compounds

Dmitri A. Chestakov, Anna M. Zawadzka, David H. Parker +3 more

A pulsed source for production of metal atoms and their oxide compounds in a supersonic expansion is described. The design utilizes a simple pulsed valve and produces a concentration of 106–107atomspercm−3 of the desired metal atoms in a molecular beam. Depending on the carrier gas used, metal compounds at similar concentration levels can also be produced.

Review of Scientific Instruments•Jan 7, 2005•2 citations

Gasdynamic method for reducing the phase volume of an atomic beam

Victor L. Varentsov, Valeriy V. Yashchuk

It is suggested that atomic and molecular beams can be thermalizd by collisions with a supersonic gas jet. (AIP)

•Feb 1, 1983•2 citations

Stationary flow conditions in pulsed supersonic beams

Wolfgang Christen

We describe a generally applicable method for the experimental determination of stationary flow conditions in pulsed supersonic beams, utilizing time-resolved electron induced fluorescence measurements of high pressure jet expansions of helium. The detection of ultraviolet photons from electronically excited helium emitted very close to the nozzle exit images the valve opening behavior-with the decided advantage that a photon signal is not affected by beam-skimmer and beam-residual gas interactions; it thus allows to conclusively determine those operation parameters of a pulsed valve that yield complete opening. The studies reveal that a "flat-top" signal, indicating constant density and commonly considered as experimental criterion for continuous flow, is insufficient. Moreover, translational temperature and mean terminal flow velocity turn out to be significantly more sensitive in testing for the equivalent behavior of a continuous nozzle source. Based on the widely distributed Even-Lavie valve we demonstrate that, in principle, it is possible to achieve quasi-continuous flow conditions even with fast-acting valves; however, the two prerequisites are a minimum pulse duration that is much longer than standard practice and previous estimates, and a suitable tagging of the appropriate beam segment.

The Journal of Chemical Physics•Oct 17, 2013•13 citations

Supersonic molecular beams production and temperature distribution in free expanding jets

G. Scoles, Franco Torello

Meccanica•Mar 1, 1968•7 citations

Sub-Kelvin Collision Temperatures in Merged Neutral Beams by Correlation in Phase-Space

Yuval Shagam, Edvardas Narevicius

Recent merged neutral beam experiments have introduced the possibility of measuring reactive collisions in the cold regime down to 10 mK. The lowest temperature attained in these experiments cannot be explained using the standard formalism developed for crossed molecular beam scattering. These low temperatures become accessible because pulsed supersonic beams develop a correlation in velocity-position space during free propagation such that the local velocity standard deviation decreases. This effect is responsible for a reduction in the attainable collision energy by more than 2 orders of magnitude along with an order of magnitude improvement in the resolution. We show that supersonic nozzles with short pulsed opening durations compared to the time-of-flight, such as the Even-Lavie valve, have a clear advantage in achieving low collision energies with improved resolution. We discuss possible improvements in the energy resolution by varying the detection time duration.

The Journal of Physical Chemistry C•Jul 29, 2013•48 citations
We describe a generally applicable method for the experimental determination of stationary flow conditions in pulsed supersonic beams, utilizing time-resolved electron induced fluorescence measurements of high pressure jet expansions of helium. The detection of ultraviolet photons from electronically excited helium emitted very close to the nozzle exit images the valve opening behavior-with the decided advantage that a photon signal is not affected by beam-skimmer and beam-residual gas interactions; it thus allows to conclusively determine those operation parameters of a pulsed valve that yield complete opening. The studies reveal that a "flat-top" signal, indicating constant density and commonly considered as experimental criterion for continuous flow, is insufficient. Moreover, translational temperature and mean terminal flow velocity turn out to be significantly more sensitive in testing for the equivalent behavior of a continuous nozzle source. Based on the widely distributed Even-Lavie valve we demonstrate that, in principle, it is possible to achieve quasi-continuous flow conditions even with fast-acting valves; however, the two prerequisites are a minimum pulse duration that is much longer than standard practice and previous estimates, and a suitable tagging of the appropriate beam segment.
Recent merged neutral beam experiments have introduced the possibility of measuring reactive collisions in the cold regime down to 10 mK. The lowest temperature attained in these experiments cannot be explained using the standard formalism developed for crossed molecular beam scattering. These low temperatures become accessible because pulsed supersonic beams develop a correlation in velocity-position space during free propagation such that the local velocity standard deviation decreases. This effect is responsible for a reduction in the attainable collision energy by more than 2 orders of magnitude along with an order of magnitude improvement in the resolution. We show that supersonic nozzles with short pulsed opening durations compared to the time-of-flight, such as the Even-Lavie valve, have a clear advantage in achieving low collision energies with improved resolution. We discuss possible improvements in the energy resolution by varying the detection time duration.