A Paul trap has been constructed for laser spectroscopic studies of the isotope shifts (IS) and hyperfine structures (hfs) of radioactive isotopes. With a sample placed near the inner surface of the ring electrode, the target atoms are evaporated by a Nd:YAG laser pulse, and then selectively ionized inside the trap by a synchronized dye laser pulse through resonance ionization spectroscopy (RIS). A cw beam from a ring dye laser is used to probe the ions, and laser-induced fluorescence (LIF) is monitored for spectroscopic measurements. The stored ions can also be analyzed by the ion-ejection time-of-flight spectrum. With an ultra-high vacuum base pressure, Hf ion storage times of one hour can be readily achieved by introducing H$ sb2$ as a buffer gas. It is demonstrated that with a very dilute sample, Hf ions can be accumulated in the trap through successive heating and RIS pulses. Through LIF measurements, both the ion cooling time and the dependence of the mean ion kinetic energy on the RF phase and trap operating conditions have been studied. A phase-locked counting technique has been applied to improve the spectroscopic resolution. The hfs of $ sp{177}$Hf and $ sp{179}$Hf with the transition a $ rm sp2D sb{3/2}$--$z sp4{ rm F} sbsp{5/2}{ circ} ( lambda$ = 340 nm) in HfII has been studied with a resolution of about 1 GHz, and their hfs A and B constants have been deduced. The IS of the radioactive $ sp{172}$Hf has been carried out with a sample containing $7 times10 sp{11} sp{172}$Hf atoms. Based on the observation of the laser-induced formation of HfH, a new spectroscopic method capable of selectively suppressing the ion population of a particular contaminant isotope has been developed to enhance the $ sp{172}$Hf signal-to-noise ratio. Deduced changes of mean-square nuclear charge radii in Hf, together with the existing data in the literature, are discussed and compared with theoretical variations obtained from Finite-Range Droplet Model calculations.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.40301 |
| Date | January 1995 |
| Creators | Zhao, Wenzheng |
| Contributors | Lee, Jonathan K. P. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001487278, proquestno: NN12521, Theses scanned by UMI/ProQuest. |
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