links for 2008-04-17

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  1. Collar, JI, et al., Science 319(5865) 933 (2007)
    “Spin-Dependent WIMP Limits from a Bubble Chamber”

    Sensitivity, selectivity, modest cost, and active medium Enviro-whiner hissy fit CF3I. Large scale apparatus using perfluorobutane is exciting.

    Like 100,000 gallons of perchloroethylene buried 4900 feet deep, it lacks the looming visceral thrill of dropping a hex nut and blasting South Dakota into space. Uncle Al recommends a Media darling active medium: iodine heptafluoride, IF7.

    CF3I,
    bp -32.5°C, d = 2.36 g/ml
    @ 25°C, d = 2.06 g/ml liquid
    29.092 wt-% F, 64.777 wt-% I

    IF7,
    mp = 4.5 C d = 2.7 g/cm^3 (solid)
    bp = 4.77 C, colorless
    51.171 wt-% F, 48.829 wt-% I

    Incompatible with Pyrex, fused silica (Teflon AF windows?), and most metals (Monel?); expensive, corrosive, toxic, malodorous. IF7 has it all!

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