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Title: Design and performance of an apparatus to generate helium droplets
Author: Curtis, Sharon.
ISNI:       0000 0001 3400 8500
Awarding Body: University of Sussex
Current Institution: University of Sussex
Date of Award: 2004
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This thesis extensively outlines the design and performance of the fIrst helium droplet apparatus to be built in the United Kingdom. Helium clusters (6000 atoms) were generated: by adiabatic expansion of research grade (99.9999%) 4He, at a stagnation pressure of 20bar, through a 5flm nozzle, cooled to 12K. The helium droplet beam is collimated by a 0.5mm skimmer (Molecular Beam Dynamics) before entering a 'pick-up' cell (lOcm, length) where the cluster beam interacts with a gaseous species of spectroscopic interest. The droplets 'pick-up' singular or multiple molecules that release their relative kinetic and potential energies to the droplet and become thermalised to the ultra cold environment of the helium bath (0.38K). Helium droplets therefore provide a cold, largely noninteractive medium in which to study the spectroscopy of molecular species. Contained in this thesis is a description: of the experimental challenge to produce a cluster source able to perform at the extreme conditions required to produce helium droplets; the modifIcations of the 'pick-up' system such that a variety of species (gases, liquids and solids) can be studied; the design and construction of a LIF region; the upgrade of a quadrupole mass spectrometer for maximum utility for this application; a description of the laser system and data acquisition methods; a review of cluster and helium droplet research; the theory associated with cluster and especially helium droplet generation; characterisation of the helium droplet beam, 'pickup' and fragmentation of neutral species upon detection; the preliminary results obtained from a study of resonant photon absorption (UV) of benzene solvated by helium droplets and the fIrst evidence of multiphoton ionisation of a molecule in a helium droplet
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available