Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams

The Review of Scientific Instruments
Yunteng HeWei Kong

Abstract

We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He2(+) and He4(+), which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl4 doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He)(n)C(+), (He)(n)Cl(+), and (He)(n)CCl(+). Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets.

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Citations

Jun 17, 2016·The Journal of Chemical Physics·Jie ZhangWei Kong
Feb 3, 2018·The Journal of Chemical Physics·Jordan FineAndrey F Vilesov
Oct 9, 2019·The Journal of Chemical Physics·Maha AlghamdiWei Kong
May 17, 2021·Mass Spectrometry Reviews·Simon AlbertiniPaul Scheier
Aug 22, 2017·The Journal of Physical Chemistry. a·Maha AlghamdiWei Kong
Aug 28, 2021·The Journal of Physical Chemistry. a·F LaimerP Scheier

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