Helium NanoDroplets Isolation (HENDI) Spectrometer

Home-built HENDI spectrometer 

The expansion chamber hosts a two-stage cold head (Sumitomo Cryogenics, CH210 cold head with F-70 H compressor) with a minimum achievable temperature of 10 K at the second stage. A nozzle plate with a 5-micron orifice is attached to the second stage. The helium nanodroplet beams are generated by expanding ultrapure helium gas (99.9999 % purity, backing pressure: 20-60 bar) through the nozzle precooled to 10-20 K. The generated helium nanodroplets have an equilibrium temperature of 0.37 K and are superfluid. These superfluid droplets pass through three "pick-up chambers" and one "buffer chamber" and are finally detected by a quadrupole mass spectrometer (Hiden analytics, mass range 1-510 amu) connected to the last chamber. The expansion chamber and the first pickup chamber are connected through a skimmer of 0.5 mm diameter. The droplet beams pass through the skimmer and enter the first pickup chamber. The three pickup chambers can be used to dope the droplets with three different molecular species of interest. The partial pressure of each of the species in these chambers is controlled using high-precision variable leak valves. In this way, the isolation of single molecules and the formation of small to large molecular clusters made up of different molecular species can be achieved.

 Mass-selective-high-resolution infrared spectroscopy of the formed molecular clusters is performed using a CW-OPO laser system (spectral range: ~2550-4500 cm-1 , resolution ~0.0001 cm-1 ).