title: Phase transition to an opaque plasma in a sonoluminescing bubble.
abstract: Time-resolved spectrum measurements of a sonoluminescing Xe bubble reveal a transition from transparency to an opaque Planck blackbody. As the temperature is <10 000  K and the density is below liquid density, the photon scattering length is 10 000 times too large to explain its opacity. We resolve this issue with a model that reduces the ionization potential. According to this model, sonoluminescence originates in a new phase of matter with high ionization. Analysis of line emission from Xe* also yields evidence of phase segregation for this first-order transition inside a bubble.
authors.affiliation: Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA. kappus@physics.ucla.edu
authors.forename: Brian
authors.initials: B
authors.lastname: Kappus
authors.forename: Shahzad
authors.initials: S
authors.lastname: Khalid
authors.forename: Avik
authors.initials: A
authors.lastname: Chakravarty
authors.forename: Seth
authors.initials: S
authors.lastname: Putterman