E-dep of Mu formation in Cryocrystals

• Condensed Rare Gases

  • Liquid neon (l-Ne) as compared with
  • Solid neon (s-Ne)

  • Liqid argon (l-Ar)
  • Solid argon (s-Ar)

  • Solid krypton (s-Kr) and Solid xenon (s-Xe) were earlier thought to show no detectable E-dependence of the Mu formation probability, which is close to 100% in each case. However, the first data were taken with constant external electric field, which caused charge buildup to cancel the internal electric field. When the experiment on s-Kr was repeated at ISIS in 2001 with rapidly switched E polarity the results were much like those in s-Ar except an even lower E>0 was needed to prevent DMF, suggesting a longer mean distance between the µ⁺ and the nearest radiolysis electron(s). The ISIS results on s-Xe show a much weaker, but significant, E-dependence, consistent with either a very short µ⁺-e^- distance or a large "prompt" (epithermal) Mu fraction, or both.

• Molecular Solids

  • Solid nitrogen (s-N₂)

  • Dry ice (s-CO₂)

  • Solid deuteromethane (s-CD₄) compared with s-N₂ and the RGS.