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Despite a pioneering study by Vilesov and co-workers some years ago, the development and application of pulsed helium droplet sources has been somewhat neglected by the helium nanodroplet community. A weakness of the very first pulsed source was a strange dependence of the mean droplet size on source conditions (temperature and helium stagnation pressure). In our laboratory we have carried out further work with pulsed sources and will show that systematic control of the mean droplet size with source conditions, entirely akin to those achievable with continuous sources, is possible through the use of a carefully designed nozzle. Furthermore, instead of changing source conditions to select different droplet sizes, a much faster alternative becomes possible with a pulsed source, namely time-resolved probing of the droplet pulse. Applications of the pulsed source in the study of a variety of molecular clusters will be presented, including water clusters.Despite a pioneering study by Vilesov and co-workers some years ago, the development and application of pulsed helium droplet sources has been somewhat neglected by the helium nanodroplet community. A weakness of the very first pulsed source was a strange dependence of the mean droplet size on source conditions (temperature and helium stagnation pressure). In our laboratory we have carried out further work with pulsed sources and will show that systematic control of the mean droplet size with source conditions, entirely akin to those achievable with continuous sources, is possible through the use of a carefully designed nozzle. Furthermore, instead of changing source conditions to select different droplet sizes, a much faster alternative becomes possible with a pulsed source, namely time-resolved probing of the droplet pulse. Applications of the pulsed source in the study of a variety of molecular clusters will be presented, including water clusters. |
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