Control of molecular rotation in superfluid helium
department or school: Science, Faculty of
department or school: Physics and Astronomy, Department of
data provider: DSpace
degree campus: UBCV
creator: MacPhail-Bartley, Ian David
issued: 2024-06-17T08:06:25Z
issued: 2024
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: This work outlines the control of molecular rotation in superfluid helium using nonresonant laser fields. Experiments within bulk superfluid helium-4 demonstrate control over the rotational frequency and direction of rotation of electronically excited helium dimers (excimers), which are created in nanometre-scale bubbles in the fluid. The excimers rotate for thousands of rotational periods, indicating relatively weak but nonzero coupling to the surrounding helium. Controlling the rotation of molecules therefore serves as a probe of superfluid helium, and its coupling to impurities. The weak coupling is attributed to the fact that helium dimers rotate with rotational energy well above that of the expected excitations of the surrounding helium. By studying other molecules embedded in helium nanodroplets, we are able to explore the rotation of molecules below, near, and above this energy scale. The influence of strong coupling to the helium becomes extreme when the energies are comparable, severely distorting observed rotational spectra. Results presented here demonstrate that the rotation of molecules in helium nanodroplets may be controlled in the same manner as molecules in the gas phase. Experiments using an optical centrifuge to attempt to control molecular rotation in helium nanodroplets, and analysis regarding the results, are presented, as well as the first experiments studying rotationally excited nitrogen in helium nanodroplets. Experimental results on rotationally exciting nitric oxide dimers in helium nanodroplets show that (NO)₂ may be a suitable candidate as a molecule for further study. Alignment of the molecule offers insights to its anisotropic polarizability, and upon excitation of long-lasting rotation, exhibits exhibits a stronger observable than previously-studied molecules whose rotational energy may be controlled within the desired range.
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/88470
note: Control of Molecular Rotation in Superfluid HeliumbyIan David MacPhail-BartleyHBSc Physics, Lakehead University, 2017A THESIS SUBMITTED IN PARTIAL FULFILLMENTOF THE REQUIREMENTS FOR THE DEGREE OFDoctor of PhilosophyinTHE FACULTY OF GRADUATE AND POSTDOCTORALSTUDIES(Physics)The University of British Columbia(Vancouver)June 2024© Ian David MacPhail-Bartley, 2024The following individuals certify that they have read, and recommend to the Fac-ulty of Graduate and Postdoctoral Studies for acceptance, the thesis entitled:Control of Molecular Rotation in Superfluid Heliumsubmitted by Ian David MacPhail-Bartley in partial fulfillment of the require-ments for the degree of Doctor of Philosophy in Physics.Examining Committee:Valery Milner, Associate Professor, Physics, UBCSupervisorKirk Madison, Associate Professor, Physics, UBCSupervisory Committee MemberFrank Stienkemeier, Professor, Physics, University of FreiburgSupervisory Committee MemberEd Grant, Professor, Chemistry, UBCUniversity ExaminerTakamasa Momose, Professor, Chemistry, UBCUniversity ExaminerHenrik Stapelfeldt, Professor, Chemistry, Aarhus UniversityExternal ExaminerAdditional Supervisory Committee Members:Roman Krems, Professor, Chemistry, UBCSupervisory Committee MemberiiAbstractThis work outlines the control of molecular rotation in superfluid helium usingnonresonant laser fields. Experiments within bulk superfluid 4He demonstrate con-trol over the rotational frequency and direction of rotation of electronically excitedhelium dimers (excimers), which are created in nanometre-scale bubbles in thefluid. The excimers rotate for thousands of rotational periods, indicating relativelyweak but nonzero coupling to the surrounding helium. Controlling the rotation ofmolecules therefore serves as a probe of superfluid helium, and its coupling to im-purities. The weak coupling is attributed to the fact that helium dimers rotate withrotational energy well above that of the expected excitations of the surroundinghelium.By s…
has type: Thesis/Dissertation
date issued: 2024-11
is shown at: 10.14288/1.0443974
language: eng
degree discipline: Physics
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-ShareAlike 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-sa/4.0/
scholar level: Graduate
contributor: Milner, Valery
type: Text
identifier URI: http://hdl.handle.net/2429/88470