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Title: Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets

Abstract

We present an experimental investigation of the effect of kinetic energy on the ion doping efficiency of superfluid helium droplets using cesium cations from a thermionic emission source. The kinetic energy of Cs{sup +} is controlled by the bias voltage of a collection grid collinearly arranged with the droplet beam. Efficient doping from ions with kinetic energies from 20 eV up to 480 V has been observed in different sized helium droplets. The relative ion doping efficiency is determined by both the kinetic energy of the ions and the average size of the droplet beam. At a fixed source temperature, the number of doped droplets increases with increasing grid voltage, while the relative ion doping efficiency decreases. This result implies that not all ions are captured upon encountering with a sufficiently large droplet, a deviation from the near unity doping efficiency for closed shell neutral molecules. We propose that this drop in ion doping efficiency with kinetic energy is related to the limited deceleration rate inside a helium droplet. When the source temperature changes from 14 K to 17 K, the relative ion doping efficiency decreases rapidly, perhaps due to the lack of viable sized droplets. The size distribution ofmore » the Cs{sup +}-doped droplet beam can be measured by deflection and by energy filtering. The observed doped droplet size is about 5 × 10{sup 6} helium atoms when the source temperature is between 14 K and 17 K.« less

Authors:
; ; ;  [1]
  1. Department of Chemistry, Oregon State University, Corvallis, Oregon 97331 (United States)
Publication Date:
OSTI Identifier:
22493460
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 143; Journal Issue: 4; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ATOMS; CAPTURE; CATIONS; CESIUM; CESIUM IONS; DOPED MATERIALS; DROPLETS; EFFICIENCY; ELECTRIC POTENTIAL; EV RANGE; HELIUM; KINETIC ENERGY; MOLECULES; SUPERFLUIDITY; TEMPERATURE RANGE 0000-0013 K; THERMIONIC EMISSION

Citation Formats

Chen, Lei, Zhang, Jie, Freund, William M., and Kong, Wei. Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets. United States: N. p., 2015. Web. doi:10.1063/1.4927471.
Chen, Lei, Zhang, Jie, Freund, William M., & Kong, Wei. Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets. United States. https://doi.org/10.1063/1.4927471
Chen, Lei, Zhang, Jie, Freund, William M., and Kong, Wei. 2015. "Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets". United States. https://doi.org/10.1063/1.4927471.
@article{osti_22493460,
title = {Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets},
author = {Chen, Lei and Zhang, Jie and Freund, William M. and Kong, Wei},
abstractNote = {We present an experimental investigation of the effect of kinetic energy on the ion doping efficiency of superfluid helium droplets using cesium cations from a thermionic emission source. The kinetic energy of Cs{sup +} is controlled by the bias voltage of a collection grid collinearly arranged with the droplet beam. Efficient doping from ions with kinetic energies from 20 eV up to 480 V has been observed in different sized helium droplets. The relative ion doping efficiency is determined by both the kinetic energy of the ions and the average size of the droplet beam. At a fixed source temperature, the number of doped droplets increases with increasing grid voltage, while the relative ion doping efficiency decreases. This result implies that not all ions are captured upon encountering with a sufficiently large droplet, a deviation from the near unity doping efficiency for closed shell neutral molecules. We propose that this drop in ion doping efficiency with kinetic energy is related to the limited deceleration rate inside a helium droplet. When the source temperature changes from 14 K to 17 K, the relative ion doping efficiency decreases rapidly, perhaps due to the lack of viable sized droplets. The size distribution of the Cs{sup +}-doped droplet beam can be measured by deflection and by energy filtering. The observed doped droplet size is about 5 × 10{sup 6} helium atoms when the source temperature is between 14 K and 17 K.},
doi = {10.1063/1.4927471},
url = {https://www.osti.gov/biblio/22493460}, journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 4,
volume = 143,
place = {United States},
year = {Tue Jul 28 00:00:00 EDT 2015},
month = {Tue Jul 28 00:00:00 EDT 2015}
}