Pulsed beam of extremely large helium droplets

摘要

Highlights?A cryogenic pulsed valve succeeds in producing micron-size huge helium droplets.?Realization of the supercritical expansion is clearly indicated firstly in pulsed form.?Other pulsed techniques should be easily combined for exploring new nano-science.AbstractWe generated a pulsed helium droplet beam with average droplet diameters of up to 2μm using a solenoid pulsed valve operated at temperatures as low as 7K. The droplet diameter was controllable over two orders of magnitude, or six orders of the number of atoms per droplet, by lowering the valve temperature from 21 to 7K. A sudden droplet size change attributed to the so-called “supercritical expansion” was firstly observed in pulsed mode, which is necessary to obtain the micrometer-scale droplets. This beam source is beneficial for experiments that require extremely large helium droplets in intense, pulsed form.]]>