May 2003

D.Phil in Chemistry - The Electronic Spectrum of Selenium Dioxide

Corpus Christi College, University of Oxford.

June 1999

M.Chem (Hons) in Chemistry

Part II project – The Electronic Spectrum of Copper Dichloride

Corpus Christi College, University of Oxford.

My research focuses on using the RELAX mass spectrometer to analyse xenon isotope ratios in a variety of solar system materials.

RELAX (Refrigerator Enhanced Laser Analyser for Xenon) is an ultra sensitive, time of flight, resonance ionisation mass spectrometer specifically for measuring xenon isotope ratios. RELAX combines

• a resonance ionisation source,
• a cryogenic sample concentrator and
• a time of flight mass spectrometer.

It is the most sensitive, and lowest blank, instrument currently available for determination of xenon isotope ratios - the detection limit is 950 atoms¹³²Xe, and is limitedonly by variation in the blank, which is currently ~1000 atoms ¹³²Xe. At peak sensitivity sample sizes are restricted to ~10⁶atoms. Repeat analyses of air calibration samples are reproducible, allowing precise and accurate isotope ratios to be determined by averaging multiple analyses.

Xenon isotope measurement made using RELAX had contributed to our understanding of a range of issues relating to the evolution of our solar system.

Most recently my research has focused on analysing material returned by NASA's Genesis missions. We have successfully extracted solar wind xenon from silicon collector targets which flew onboard the Genesis spacecraft, and determined the xenon concentration and isotopic composition.

I am also interested in a wide range of other samples which can be analysed using RELAX, including:

• Analysis of individual hadean zircons to constrain the Pu/U ratio of the early solar system.
• Analysis of individual lunar zircons
• Investigationf of Xe concentrations of IDPs, which suggest the concentration may had a significantly lower upper limit than previously reported.
• We have attempted Xe analysis of individual SiC grains.
• I-Xe dating of a wide range of meteorites, including material of different metamorphic grades from Rumuruti chondrites to investigate whether there is a link between the time of clousre to Xe-loss and the extend of metamorphism on the R-chindrite parent body.
• Comparing the I-Xe systematics in anomalous eucrites to that in "normal" eucrites.

We are currently working towards attempting xenon analysis of cometary material collected and returned to earth by NASA's Stardust mission. The aerogel used to collect the cometary particles has a large Xe blank that would swamp any embedded cometary Xe, therefore we are in the process of combining closed system step etching (CSSE) with RELAX to attempt to separate the xenon in the aerogel from that in the cometary material.

• Isotope Geochemistry and Cosmochemistry