An optical study of Mn and Mo isotopes has been performed in two contrasting regions of the nuclear chart. Collinear laser spectroscopic methods were employed using the Ion Guide Separator On-Line (IGISOL) at the University of Jyväskylä, Finland. Optical pumping in an ion-trap with the use of frequency quadrupled titanium sapphire lasers, greatly improved the efficiency of the spectroscopy performed.For the first time, the change in mean-square charge radius was determined for ground and isomeric states in 50-56Mn with a sharp shell closure seen across N = 28. Nuclear quadrupole moments in 50m,53,54,56Mn were also extracted, displaying trends similar to those of the charge radii. Newly extracted hyperfine structures and isotope shifts of 90-92,94-98,100,102-106,108Mo span the N = 50 shell closure and well-known N = 60 shape change. Unlike the Z = 38 - 41 isotopic chains, Mo exhibits a smooth increase in mean-square charge radius, with no sudden onset of deformation at N = 60. These measurements signify the end point of this strongly deformed A ~ 100 region in both Z and N. In the Z ~ 40 region, the charge radii follow the trends in the mass measurements near perfectly. However, in the Mn measurements a clear disparity between the mass and charge radii measurements is seen across the N = 28 magic shell closure. The absence of any shell effects in the Mn mass measurements show the importance of charge radii measurements, with pertinent implications for future investigations in the N = 40 region. Additionally, a portable data acquisition system for laser spectroscopy has been successfully tested. It is based on the LabJack system which will directly interface to a USB connection. It is able to register individual photons from amplified and converted photomultiplier tube signals (with bunched or continuous ion beams). The device drives a Cooknell voltage supply, which steps the voltage across the laser-ion interaction region. The introduction of an accurate 100 ms time window into the LabJack system has enabled a precise photon detection system for future off-line testing and on-line use. Further to this, a new method of locating hyperfine resonances has been introduced into our spectroscopy.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:525273 |
| Date | January 2010 |
| Creators | Charlwood, Frances Claire |
| Contributors | Campbell, Paul |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/ground-state-properties-of-mn-and-mo-using-laser-spectroscopic-methods(a2cc81ce-2b0f-44a4-b926-b5091e84f9a9).html |
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