Towards rotational control of molecules in helium nanodroplets
department or school: Science, Faculty of
department or school: Physics and Astronomy, Department of
data provider: DSpace
degree campus: UBCV
creator: Fordyce, Jordan A. M.
issued: 2020-06-26T14:19:13Z
issued: 2020
related degree: Master of Science - MSc
degree grantor: University of British Columbia
description: The feasibility of using rotating molecules as “nanoprobes” for testing the superfluidity of helium nanodroplets is explored in this thesis. Helium nanodroplets have an internal temperature of 0.37 K and are below the superfluid transition temperature in bulk helium of 2.17 K. The onset of superfluidity in this microscopic environment will be explored by rotationally exciting molecules using a tool called an optical centrifuge. This tool affords a high degree of precision in the final rotational frequency that the molecule will reach and makes it useful in probing the coupling between the rotor and helium. A unique helium nanodroplet vacuum chamber system was characterized for the range of operation possible, especially with focus on the signal to background detection conditions. Two techniques were explored to characterize the dynamical rotational behaviour of the molecules in these conditions: direct measurement of the molecular orientation and direct measurement of the angular momentum state. The molecular orientation of a molecule is characterized by it’s confinement to the rotational plane using ⟨cos² θ2D⟩ as the metric. A ⟨cos² θ2D⟩ measurement of ≈ 0.7 was successfully recovered from background for carbon disulfide doped helium droplets using an alignment probe pulse, however, with the centrifuge it was ultimately unclear if the molecule was rotating or simply aligning to the plane of rotation. The angular momenta of a molecule was characterized via its ion signal from a Resonance Enhanced Multiphoton Ionization (REMPI) scheme. The feasibility of measuring a transition in oxygen at the low signal to background densities was studied and would be promising to use with oxygen doped helium droplets. In order to continue the research, improvements need to be made to the set up and the two techniques should be used in tandem so that rotation can be better detected and characterized.
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/74794
note: TOWARDS ROTATIONAL CONTROL OFMOLECULES IN HELIUM NANODROPLETSbyJordan A. M. FordyceB.Sc., University of Alberta, 2015A THESIS SUBMITTED IN PARTIAL FULFILLMENTOF THE REQUIREMENTS FOR THE DEGREE OFMaster of ScienceinTHE FACULTY OF GRADUATE AND POSTDOCTORALSTUDIES(Physics)The University of British Columbia(Vancouver)June 2020c© Jordan A. M. Fordyce, 2020The following individuals certify that they have read, and recommend to the Facultyof Graduate and Postdoctoral Studies for acceptance, the thesis entitled:TOWARDSROTATIONALCONTROLOFMOLECULES INHELIUMNANODROPLETSsubmitted by Jordan A. M. Fordyce in partial fulfillment of the requirements forthe degree of Master of Science in Physics.Examining Committee:Dr. Valery Milner, PhysicsSupervisorDr. Takamasa Momose, ChemistrySupervisory Committee MemberiiAbstractThe feasibility of using rotating molecules as “nanoprobes” for testing the superflu-idity of helium nanodroplets is explored in this thesis. Helium nanodroplets have aninternal temperature of 0.37 K and are below the superfluid transition temperature inbulk helium of 2.17 K. The onset of superfluidity in this microscopic environmentwill be explored by rotationally exciting molecules using a tool called an optical cen-trifuge. This tool affords a high degree of precision in the final rotational frequencythat the molecule will reach and makes it useful in probing the coupling betweenthe rotor and helium. A unique helium nanodroplet vacuum chamber system wascharacterized for the range of operation possible, especially with focus on the signalto background detection conditions. Two techniques were explored to characterizethe dynamical rotational behaviour of the molecules in these conditions: directmeasurement of the molecular orientation and direct measurement of the angularmomentum state. The molecular orientation of a molecule is characterized by it’sconfinement to the rotational plane using 〈cos2 θ2D〉 as the metric. A 〈cos2 θ2D〉measurement of ≈ 0.7 was successfully rec…
has type: Thesis/Dissertation
date issued: 2020-11
is shown at: 10.14288/1.0392000
language: eng
degree discipline: Physics
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/74794