Development of a Pulsed Helium Droplet Spectrometer

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With support from the Chemistry Research Instrumentation and Facilities (CRIF) Program, Prof. Andrey F. Vilesov of the University of Southern California will develop a state-of-the-art pulsed helium droplet spectrometer. He will develop and optimize experimental methods for the generation of pulsed (50-100 microseconds) helium droplet beams in order to achieve a factor of 100 - 10,000 higher intensity as compared to contemporary continuous-wave beams. To fully exploit this advantage, he will mate the developed source with other modern pulsed experimental techniques such as infrared depletion spectroscopy, laser-induced fluorescence, laser photolysis, laser ablation, and time-of-flight (TOF) mass spectroscopy. This will facilitate new experiments involving helium droplets, such as (i) studies of large bio-molecules; (ii) assembly and interrogation of large metal and molecular clusters; (iii) pump-probe experiments; (iv) studies of photochemical reactions; and (v) generation and use of very large droplets containing over 100 million atoms. This development will help to establish He droplet spectroscopy as a versatile new tool, will make it cost-effective, and will make the technique immediately accessible to mainstream scientists. The ultimate goal is the development of a pulsed helium droplet beam apparatus based on a closed-cycle refrigerator, equipped with pulsed infrared laser and a TOF mass spectrometer. Graduate students will be involved in all phases, and will use the instrument as a training ground prior to integrating the pulsed nozzle in their own experiments. This system will enable advances to be achieved that are not presently possible. Other chemists interested in spectroscopy, analytics and low temperature chemical reactivity and dynamics can also benefit greatly from this user-friendly and cost-effective source. Utilization to more applied areas such as interrogation of large biomolecules or development of new nano-materials is anticipated.